Bucha residents face the aftermath of the carnage as they fear the return of Russian forces.

Halyna Matiushko knows that her son is dead. She knows that Serhii Matiushko was found with four other men dead on a basement floor in Bucha, a town on the western fringe of kyiv that has become synonymous with Russian atrocities. She knows that Ukraine’s Prosecutor General Iryna Venediktova has called that basement a “torture chamber.”

She knows that the photos sent to her by the police show her dead son with a gaunt face and what appear to be broken teeth. Her hands are tied behind her back. He was, police have said, shot to death.

What Ms. Matiushko does not know, what she cannot understand, is how this could have happened.

“He was a normal worker,” Matiushko told The Globe and Mail on Tuesday. “He was not any kind of threat to the military.”

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Serhii, a divorced father with a 20-year-old son, lived near Hostomel Airport, a major military facility that Russian forces tried to seize at the start of their invasion of Ukraine. Surrounded by fierce fighting, he stayed home and helped care for two elderly women in his apartment complex.

But he also made plans to leave for Ivano-Frankivsk, a city almost 600 kilometers away by road, to enlist in the fight. He planned to catch a bus on March 12.

However, as he was preparing to leave, a local volunteer asked him to help him move some cargo. When he finished that job, the bus was gone.

Mrs. Matiushko never heard from Serhii again. On the day of her scheduled departure, she walked two hours through heavy shelling to Hostomel, but she was unable to locate him. She learned from others that the local volunteer’s car had been found marked with a V, a symbol used by Russian forces in the invasion of Ukraine. Other Ukrainian communities reported that Russian soldiers stole cars and then marked them with a V.

For almost a month, Ms. Matiushko tried to find Serhii, posting pleas on Facebook. She didn’t hear anything. Then, earlier this week, police sent images of the men discovered in the basement. Mrs. Matiushko instantly recognized her son’s face and the clothes she was wearing.

The slaughter of civilians in Bucha, and in particular of those like Serhii shot with their hands tied behind their backs, has created a new fury against Russia. It has prompted the imposition of additional European sanctions, calls by Canada, the United States and others to suspend Russia from the United Nations Human Rights Council, and commitments by Ukraine and major Western democracies to investigate alleged war crimes.

“They are not even war crimes,” Matiushko said of those who killed his son. “It’s the people who are crazy. In a war, warriors shoot warriors. Here they shoot normal humans.

On Tuesday, Ukraine’s President Volodymyr Zelensky said a war crimes tribunal like the one held in Nuremberg after World War II is needed to examine Russian actions. In a speech to the UN Security Council, he gave a graphic description of what the Ukrainian authorities have uncovered in recent days.

People “were thrown into wells, so they died there suffering. They were killed in their apartments, houses, blown up by grenades. Civilians were crushed by tanks while sitting in their cars in the middle of the road, just for their pleasure,” he said.

“The women were raped and murdered in front of their children. They ripped out their tongues just because the assailant didn’t hear what they wanted to hear from them.”

He warned that the atrocities uncovered in Bucha would also be found in other parts of Ukraine, where the city of Mariupol remains under siege, Kherson and surrounding areas remain under Russian occupation, and Kharkiv is bracing for a new expected military attack.

Russian Foreign Minister Sergey Lavrov accused Western countries of promoting “hysteria” to “find a pretext to break up the ongoing negotiations” between Moscow and kyiv, he said. Russia’s ambassador to the United Nations, Vassily Nebenzia, dismissed Zelensky’s comments as “a lot of lies.”

But the streets of Bucha remain for Ukraine the most vivid illustration of Russian war behavior. On Tuesday, officials led foreign journalists through the city, showing them a pile of six mutilated bodies, empty eye sockets peering through fire-charred skin. Four were women, one of them small enough to be a girl. One showed clear evidence of having been hit by a bullet, kyiv Police Chief Andrii Nebytov said.

“They executed the people they found, then they burned them to hide the crime,” he said.

“Calling the Russians ‘beasts’ would be a nice description of them,” said Bucha resident Larysa Savenko.

She lives on Vokzalna Street, where residents counted 72 vehicles, many of them armored, in a Russian convoy that passed on February 27 heading for kyiv. When Ukrainian forces attacked, the ensuing battle turned the street in front of Ms Savenko’s door into a metal graveyard, with heavily armored corpses still in place as a memorial to one of the most important early battles of the war.

The fighting on Vokzalna Street destroyed many houses and damaged the roof and walls of Ms. Savenko’s house. Without electricity or other basic services for weeks, she survived on frozen meat and lard stored in a ditch dug in her backyard.

The flight of Russian forces in recent days has done little to calm their fears. “The most important thing for me is that they don’t come back a second time, like they did in Chechnya. That’s scary,” she said.

In fact, although the fighting has ceased, the war in Bucha is far from over. Twenty-five demining workers are now scouring the area for explosives. By Tuesday afternoon, they had located 1,126 potentially explosive devices, including bullets and an unexploded cruise missile.

Millions of hectares of Ukraine will need to be searched for mines, officials said Tuesday.

But sweeping a small area of ​​downtown Bucha took five days, said Petro Kiselyov, deputy director of the kyiv region of the State Emergency Service. That effort revealed rigged grenades in four apartments, at least one of which appeared to belong to a Ukrainian soldier. Mr. Kiselyov said that he had seen three booby-trapped bodies, with live grenades hidden under the arms of the corpses.

“Russia, Ukraine and Belarus were sister countries,” he said. “It’s amazing to see this.”

Ms. Matiushko also finds it difficult to understand. While she searched for Serhii, she also treated her other son, Roman, 42, who remains in hospital with multiple gunshot wounds. Russian soldiers sprayed him with bullets as he stood in line at a grocery store, she said. His abdomen and both hips were hit, according to a hospital report. A bullet lodged in his left hip, causing multiple fractures. Roman needs surgery and “now he is in very bad condition,” Matiushko said.

Justice must be done, he said.

“I want the truth. And I want those people punished,” she said.

On Tuesday, he traveled to Bucha to beg the police to release Serhii’s body for burial. But what happened to him should not be forgotten, he said.

“The Russians say they didn’t commit these crimes, they were just imagined,” he said, showing a photograph taken of Serhii where he was found in the basement, his face ghostly in the light of a flashlight.

“But it wasn’t imagined,” he said. “This is my Son. This is my Son.”

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