MARY LOUISE KELLY, HOST:

Fifty thousand investigations have been opened into alleged war crimes committed by Russian troops in Ukraine - 50,000 - hospital bombings, kidnappings, executions of unarmed Ukrainian civilians. Fifty thousand is a number that's hard to comprehend on its own. Oleksandra Matviichuk heads the Center for Civil Liberties. She's one of the recipients of this year's Nobel Peace Prize. She believes the numbers obscure the scale of the loss.

OLEKSANDRA MATVIICHUK: Yes, I'm a professional human rights lawyer, but first of all, I am a human being. And once I started to notice that, I started to use numbers instead names.

KELLY: Today we bring you a story from NPR's investigations team, a story that tries to address these vast numbers by focusing on just one case, one war crime, one investigation, one story that might illuminate the challenge that war crimes prosecutors face all over Ukraine. NPR's investigative correspondent Tim Mak was in the country from the very first days of the invasion as terrified Ukrainian civilians faced the Russian onslaught. He heard a rumor about a man who may have served in the French Foreign Legion brutally killed, his body lying in the streets of a village called Nova Basan for 30 days, his car burnt to ashes right next to him - a warning that this report includes graphic descriptions of his killing. Tim traveled to Nova Basan with his team to see the destroyed car where the body was rumored to have been found. A local administrator was able to point him toward a neighboring town where he said the dead man's mother lived. Her name was Oksana. Tim Mak takes the story from here.

TIM MAK, BYLINE: When we got there, Oksana welcomed us into her home.

OKSANA BREUS: (Non-English language spoken).

LUKA: Do you want coffee or tea?

MAK: We sat in her kitchen. Oksana went to get a photograph of her son and put it on the table between us.

Your son was in the French Foreign Legion. Is that correct? What was his name?

LUKA: (Non-English language spoken).

OKSANA BREUS: Oleksandr.

MAK: Oleksandr Breus. After a stint in the French Foreign Legion, he returned to Ukraine before the war broke out.

How old was Oleksandr?

LUKA: (Non-English language spoken).

OKSANA BREUS: (Non-English language spoken).

LUKA: Twenty-eight.

MAK: Twenty-eight years old.

OKSANA BREUS: (Non-English language spoken).

MAK: She told me he died on the fifth day of the war, the morning of February 28, on his way to evacuate his girlfriend and sister from Kyiv.

OKSANA BREUS: (Non-English language spoken).

MAK: She didn't know how Oleksandr was killed or who killed him. But she did have a video that showed the scene of the killing on the day of Oleksandr's death. So she played it for us.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED PERSON #1: (Non-English language spoken).

MAK: Oh, my God. Is that...

Watching the video, Oksana was overcome. And at the moment we watched it, we recognized that Oleksandr's killing was almost certainly a war crime. By all indications, he was an unarmed man in civilian clothes, brutally killed. The video shows a man lying on the ground. His left arm lies limp. And his right arm is curled up across what remains of his head. It looks like an execution. The man taking the video narrates what he's seeing.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED PERSON #1: (Non-English language spoken).

MAK: "The Russians drove through, damn it," he says. On the video, Oleksandr's body is next to the same burnt-out, destroyed car we had seen near Nova Basan. There's a large hole in the back door on the driver's side.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED PERSON #1: (Non-English language spoken).

MAK: "Poor thing," says the man on the video.

OKSANA BREUS: (Non-English language spoken).

MAK: Oksana could no longer continue.

LUKA: I think we've got to talk to her sister if you want to talk about it, I think.

MAK: Still, she wanted to show us one more thing.

OKSANA BREUS: (Non-English language spoken).

MAK: Alexander's dog, Clifford.

OKSANA BREUS: (Non-English language spoken).

MAK: "Such a handsome dog," she says. "Do you see how much he misses him?"

When we returned to Kyiv, we showed Oksana's video to an official in Ukraine's State Bureau of Investigation. He told us it was clearly a war crime. The man was not a threat, in civilian clothes, carrying no weapons and apparently facing away from the direction of the Russian advance. Oleksandr's case was one case among many that overwhelmed investigators were juggling. So we kept digging on our own. Oleksandr's mother had told us to call his sister, Anya.

I can get us some coffee.

ANYA BREUS: No, no. Thanks.

MAK: Anya and Oleksandr were very close. And she sat down with us to tell us more about him.

A BREUS: He changed his mind very often. Like, today he wants to be a basketball player. Tomorrow he wants to be a photographer. Another day, he wants to be a manager, and so on, so on.

MAK: He even had a brief stint trying to be a rapper.

(SOUNDBITE OF MUSIC)

OLEKSANDR BREUS: (Rapping in non-English language).

MAK: Oleksandr was also a passionate Ukrainian patriot, she says. He liked to debate Russians about history in online chats about the differences between Ukrainians and Russians.

A BREUS: He always watched videos about Ukrainian history. He told us all the time that Russians are awful people.

MAK: Sasha Hrusko, one of Oleksandr's best friends, remembers Oleksandr was restless in his 20s. In 2018, he joined the French Foreign Legion.

SASHA HRUSKO: He was looking for himself. He was looking for the same realization. That's why he just found out himself in the French Legion.

MAK: A career in the military suited Oleksandr well. He thrived in stressful situations. I spoke to another friend of his, Borys, a legionnaire who served with him, with the help of an interpreter.

BORYS: (Through interpreter) So he was a very calm, collected person. He was able to deal very easily with tough situations. He was very levelheaded, coolheaded. He didn't have that many friends, but when he had one, he had intense friendships.

MAK: Everyone described Oleksandr as a loyal friend. He was in the Legion for four years. Ultimately, Oleksandr left the French military in late 2021 after getting permanent residency status in France. Boyrs also told us about Oleksandr’s girlfriend, Yulia. We reached out to her, but she was too overwhelmed by grief to speak with us. Yulia and Oleksandr had tried to have a long-distance relationship, but it wasn't easy. Still, Oleksandr was committed to the relationship.

BORYS: (Through interpreter) So I am sure that he wanted to propose, but I think that he wanted to do things well, and he didn't want to rush things.

MAK: So a month before the war broke out, he decided to head back to his home country and back to Yulia. Borys shared a series of voice recordings between him and Oleksandr talking about it. Here's Oleksandr.

(SOUNDBITE OF ARCHIVED RECORDING)

OLEKSANDR BREUS: (Non-English language spoken).

MAK: He told Borys he was worried about the relationship, but he wanted to make it work. After he returned to Ukraine, he and Yulia began to reconcile. And Oleksandr began seriously talking to his friends about proposing.

(SOUNDBITE OF SIREN WAILING)

MAK: But on February 24, Russia surprised many Ukrainians by doing what had once been unthinkable.

(SOUNDBITE OF ARCHIVED RECORDING)

RACHEL MARTIN, BYLINE: That's what it sounded like in Kyiv this morning as Ukrainians faced down the reality of a Russian invasion.

(SOUNDBITE OF BOMBS EXPLODING)

MAK: In the chaos, Oleksandr brought his dog Clifford to his childhood home in Bobrovytsia. He planned to head back to the capital city, some two hours away, to evacuate his girlfriend and sister. But during the first week of the war, the Ukrainian government instituted a multi-day curfew in Kyiv, preventing him from getting back to them. The uncertain, anxious situation brought him to tears, Anya recalled.

A BREUS: He was disappointed because he want to arrive to Yulia as soon as possible, and he stayed at Bobrovytsia for two days.

MAK: And there was another thing. Russian forces were on the move. By February 28, four days into the invasion, Oleksandr began his journey towards Kyiv.

(SOUNDBITE OF MUSIC)

MAK: And so did the Russian forces.

(SOUNDBITE OF MUSIC)

KELLY: If you're just joining us, you're listening to ALL THINGS CONSIDERED from NPR News. I'm Mary Louise Kelly. We are bringing you a story today from our investigations team in Ukraine. NPR's Tim Mak has been looking into the death of Oleksandr Breus, a war crime during the Russian invasion, to try to find out how he died and who killed him. Back to Tim.

MAK: Oleksandr left his childhood home at around 8 a.m. shortly after the curfew in Kyiv was lifted. His mother saw him off. He was wearing a pair of white Nikes and loose-fitting green pants. While he was driving, his dad called to check in on him.

UNIDENTIFIED PERSON #2: (Through interpreter) I called him. I asked, where are you? He said, I'm at a checkpoint and see a column. I told Sasha, please, Sasha, please don't go there. Don't go. Head back. He said, OK, OK, and hung up.

MAK: His father was in eastern Ukraine, fighting the Russian advance. It's unclear exactly where Oleksandr was at the time.

UNIDENTIFIED PERSON #2: (Through interpreter) That's the only thing we talked about, and it's the last time we spoke.

MAK: Somewhere between 9 and 10 a.m. that morning, a number of people in the village heard a large explosion. Tetiana Baryshovets works at a local supermarket which closed early as Russian forces pressed deeper into their village. She decided to make a dash home on her bicycle, and as she rode home, she saw a car on fire. A body was lying next to it in the middle of the road.

TETIANA BARYSHOVETS: (Through interpreter) I stopped. I wanted to check if he was alive, but it was obvious that he wasn't. I didn't see the head, but the hand and legs were twisted unnaturally.

MAK: Oleksandr's green pants were partially burnt off, exposing blackened flesh below the knee. His white Nike sneakers were nowhere to be seen. The fire had burned them off.

BARYSHOVETS: (Through interpreter) I started trembling, thinking, why would they kill a person like that? I started crying. My husband was waiting for me, but I couldn't ride the bicycle anymore.

MAK: That evening Anya Breus hadn't heard from her brother. It had been hours. She began posting on social media and asking if anyone had seen him.

A BREUS: (Through interpreter) I wrote up a missing person post with a photo of my brother in his car and where he was heading.

MAK: That night a stranger passed the video of the crime scene to Anya Breus. It had been circulating on social media. After she forwarded it to Oleksandr's best friend Hrusko, he had no doubt it was Oleksandr.

FRANCO ORDOÑEZ, BYLINE: Just seeing his body, it's enough. There is nothing to be discussed. I just - you just feel it.

MAK: We knew much more about the crime than when we first started, who Oleksandr was. We'd met his family, his friends, his dog. We knew why he was on the road and roughly when he died. But still, we knew almost nothing about the essential question for war crimes prosecutors. How was he killed? For that, we would need an eyewitness.

(SOUNDBITE OF MUSIC)

MAK: We canvas houses in Nova Basan for potential eyewitnesses, but many homes weren't occupied.

OLEKSANDR HOLOD: (Non-English language spoken).

MAK: But then, a breakthrough - a man approached us.

HOLOD: (Non-English language spoken).

MAK: "I want to show you what they did to my house," he said. His name was Oleksandr Holod. We'd knocked on his door before, but he hadn't been home. This time he invited us in. His place, which stood across the street from the wreckage of Oleksandr's vehicle, was dusty and dark inside - no electronics, no carpeting and, since the war, an empty dwelling. Holod had something important to tell us. He said he was an eyewitness to the killing and began describing what he saw on the morning of February 28 as the column of Russian armored vehicles descended on his village.

HOLOD: (Through interpreter) I simply heard the noise, the increasing noise there coming. OK, the first column that I saw - it was five BTRs on the distance from one another.

MAK: As the Russian forces entered the area, he saw soldiers leave armored vehicles known as BTRs and spread out throughout the neighborhood. Later, he saw a man's car coming from the direction of Bobrovytsia. It was Oleksandr's car, the same burnt-out car right outside his home. Three BTRs were ahead of Oleksandr on the road, and he pulled up alongside the fourth.

HOLOD: (Through interpreter) He stopped the car. He exited the car. And he stood, like, in a full scale. And he started to quarrel with them about something. He started to say to them something like, what are you doing here? And why are you doing this?

MAK: As Oleksandr was talking, two soldiers positioned themselves behind him. One of the soldiers had a machine gun and another an assault rifle. The one with the rifle was tall, Holod said. And then, without warning, the soldier opened fire on Oleksandr.

HOLOD: (Through interpreter) So the guy fell on the road - brain splashed and blood. And the BTR, the No. 4 that was standing here - it turned the turret and hit the car.

MAK: That shot from the BTR destroyed the car. And that's what Holod said happened to Oleksandr.

(SOUNDBITE OF MUSIC)

MAK: Oleksandr's body lay in the street for a month as his family desperately tried to retrieve him. But the tide of war was changing. At the beginning of April, Ukrainian forces made their way into Nova Basan, meaning it was finally possible to retrieve Oleksandr's body.

(SOUNDBITE OF MUSIC)

MAK: We had pieced together what happened to Oleksandr. Finding his killers was going to be more difficult. But the smallest things can lead to a breakthrough. On Facebook, we found one more video taken from Nova Basan. It showed Russian forces moving through the village on the day Oleksandr was killed.

(SOUNDBITE OF ARCHIVED RECORDING)

OLENA BONDARENKO: (Non-English language spoken).

MAK: So we tracked down the woman who took it. Olena Bondarenko, along with her small dog, welcomed us into the furniture store where she works in Kyiv.

UNIDENTIFIED PERSON #3: (Non-English language spoken).

BONDARENKO: (Non-English language spoken).

MAK: After the war started, Bondarenko fled the capital city for the home her family owned in Nova Basan, hoping there would be less fighting in the small village. On the morning of Oleksandr's death, she stood outside in a state of shock as armored vehicles rolled by. And she showed us a second video she took. As vehicles pass by, an armed soldier appears in the frame and aims a rifle at her, causing her to gasp before firing off shots in her direction.

(SOUNDBITE OF GUN FIRING)

MAK: She drops to the floor, and her father pulls her away. Later, she noticed something unusual about the vehicles on the video.

BONDARENKO: (Through interpreter) They were new tanks with the letter O. On TV, they were only talking about Z and V. I told the Ukrainian military about these vehicles with the letter O. They were totally different. It was a different type of armored vehicle, and they wore a different colored uniform.

MAK: That O marking on the armored vehicle in Olena's video was crucial to understanding which Russian units were on the ground. We reached out to every corner of the Ukrainian government we thought might be able to help us find the units in Nova Basan - intelligence agencies, police, prosecutors - and we showed them what we'd found. They told us that the letter O meant that the vehicles were from units in Russia's central military district. In that district, there were some prime suspects. The specific units were the 15th, the 21st and the 30th. We needed more help to find out the exact brigades that were in Nova Basan the day Oleksandr was killed. There are people who track military equipment just by scouring all the information that's publicly available - people like Tom Bullock. He's an analyst at Janes, a company that monitors militaries all around the world.

TOM BULLOCK: Part of my work when I started this was building out guides for how to identify different Russian military units.

MAK: He said that the damage to Oleksandr's car in the videos matches Holod's story.

BULLOCK: So something similar to the BTR's canon could probably do similar damage.

MAK: So it would be reasonable, if we had an eyewitness who said the BTR fired on this car, that this is consistent with the damage that you see.

BULLOCK: Yes.

MAK: Next, we showed him Olena Bondarenko's videos of the Russian vehicles. Much like cars, BTRs come in all sorts of models.

BULLOCK: So in this video, you're seeing the rear of a BTR-82A.

MAK: Eighty-two A. We had another clue, and it was a crucial one.

GEORGE BARROS: The fact that we can identify that that's a BTR-82 type A is significant because there's only two brigades that actually field that equipment. And those are the 15th and the 30th Brigade.

MAK: George Barros has also been tracking Russian units daily. He works for the Institute for the Study of War. Both of our experts agreed. The armored vehicle's model revealed a lot about what was going on in Nova Basan that day. Russian military doctrine suggests that these BTRs and these brigades - the 15th and the 30th - would have been used for clearing operations.

BARROS: They're walking down the main stretch of the village, what it looks like, and they're checking, you know, house to house. They're peeking over fences. And what they're probably doing is - it's a clearing operation.

MAK: It felt like a breakthrough. We had found the units that were most likely responsible for Oleksandr's death, and inside those units was the person that pulled the trigger. How close could we get to him? The Russian troops in Nova Basan were not wearing insignia or patches that identified who they were or where they came from.

BARROS: I think what's useful to say is the Russian ground force that actually deployed to around Ukraine back in February was, like, 120,000 people.

MAK: We were trying to find just one of those 120,000 soldiers. But we narrowed our list of suspects to just two units, which had far fewer soldiers.

BARROS: So that means that we can narrow it down to a discrete pool of - we're looking at 1 to 8 battalions, which narrows down the search quite significantly.

MAK: Yeah. So we can narrow it down to about 4,000 people?

BARROS: Roughly, yeah.

MAK: Four thousand soldiers - somewhere in that group was the person we were looking for. Our eyewitness, Holod, said he saw five BTRs in the immediate vicinity when Oleksandr was killed. Each vehicle has a capacity of 10 soldiers, so the killer was among a group of about 50 people who passed through Nova Basan on the morning of February 28. But we'd reached our limit. We couldn't get the actual names of those 50. We could name one person - the military officer who was officially responsible for the units.

BARROS: It's very clear that, at that point in time in Nova Basan, we saw significant elements in that area, likely commanded by Russian Colonel General Aleksandr Lapin.

MAK: Aleksandr Lapin - the man in charge of those who killed Oleksandr and blew up his car. If all of the killings and shootings around Nova Basan are compiled, investigators could argue that the atrocities were systematic and widespread and the responsibility of the commander. They could prosecute him for war crimes. For now, we couldn't narrow it down any further, even though we had spent months conducting close to 100 interviews and developing sources. And this was just for one war crime. There are around 50,000 war crimes under investigation in Ukraine. It's an overwhelming task. Roman Avramenko heads the Ukrainian NGO Truth Hounds, which documents and investigates war crimes.

ROMAN AVRAMENKO: Frankly speaking, I think it's not possible to establish justice for all the cases of war crimes committed in the course of full-scale invasion.

MAK: So it falls to Ukrainian investigators to show that individual war crimes are part of a larger pattern. But the Ukrainian system is swamped, and there are signs that Ukraine and the world will fall short, stifled by a lack of resources, the sheer number of cases and the degradation of evidence during war. Oleksandr's story illustrates all of these aspects.

(SOUNDBITE OF FOOTSTEPS FALLING)

MAK: Four months after Oleksandr was killed, we went with his sister and mother to his grave. There were violets around the dirt mound where his body lay at rest. That day, Oleksandr's mother remembered one more thing about her son.

OKSANA BREUS: (Through interpreter) Last year, when Oleksandr - he was returning home. He was flying through Netherlands, and he knew that I loved flowers. So he had some spare time, and he bought me those tulips - seeds there. And this year, 10 out of 10 - all of them - they bloomed.

UNIDENTIFIED INTERPRETER: (Non-English language spoken).

OKSANA BREUS: (Through interpreter) So they bloomed exactly on the Mother's Day, and they were blooming exactly for 21 days.

MAK: Dutch tulips, blooming after his death. Tim Mak, NPR News.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.