Alla, 37, said that as she was sleeping in her home in the southern Ukrainian city of Mykolaiv early Thursday, she was awakened by a sudden burst of light. Then, she recounted, an acrid smell filled her nostrils as it became clear her home had been hit by a Russian strike. 

Immediately, her thoughts turned to her 11-year-old son, Artem, she said. NBC News has chosen not to divulge the last name of Alla, her husband, Ruslan, and their son for privacy and security reasons.

Artem was screaming for help and unable to move, she said, adding that a large part of their five-story building had collapsed onto his ground-floor bedroom.

“He was conscious. He tried talking to us,” Alla added. “He was in shock.”  

It took rescuers seven hours to get Artem out. His legs were broken and he was taken to a regional hospital for dialysis as his condition worsened.

But the furious efforts to keep the boy alive ultimately failed — Artem died later Thursday of heart failure, the latest victim of Russian President Vladimir Putin’s war in Ukraine.

Earlier, video shared by Ukrainian rescue officials showed Artem being pulled out of the rubble and placed on a stretcher as he moaned in pain.

The video then shows Artem's distraught father, a 42-year-old driving instructor, running alongside him and stopping to kiss him on the head before he is loaded on to an ambulance.

Their home, a humble brick building, had a gaping hole where its roof and top-floor apartments once stood. NBC News saw it just hours after it was hit by what local officials said was one of eight Russian missiles that landed in the city that night.

Russia has unleashed a barrage of deadly attacks on cities across Ukraine in recent days,  hitting the heart of the country’s capital, Kyiv, Lviv in the west and Kharkiv in the northeast, in apparent retaliation for an explosion Saturday that damaged a key bridge that connects Russia to the annexed Crimean Peninsula.

Putin said Monday that the airstrikes were in response to what he said was Kyiv’s long track record of “terrorist” actions, including the bridge blast.

After the attack on Mykolaiv, Ukrainian President Volodymyr Zelenskyy vowed that Moscow would be held responsible for every such strike. “A just punishment awaits you,” he said in a post on his Telegram channel.Blaming “Russian terrorists” for what happened, and for “ruining our lives,” Alla, now homeless, said she and her family would stay with relatives while they figure out their next steps.

Another Mykolaiv resident, Olena Myschanets, said she was fearful for the fate of her older sister, Olga, and her niece, Oksana, who she said lived on the top floor of the same building as Alla, Ruslan and Artem. 

She said they had not returned any of her messages.

“I am praying hard that they are alive,” Myschanets, 56, said as she choked back tears. She added that all she can do is hope that they somehow escaped the strike.

She said she was not aware of any military sites nearby, adding that the area is a quiet residential neighborhood. Her husband, Valeri, blamed Moscow for the destruction. “Putin and his state are terrorists that must be destroyed,” he said.

Russia has denied targeting civilians, though the wave of aerial attacks it unleashed this week hit civilian areas and critical infrastructure across the country.

Artem's father returned to the family's destroyed apartment early Friday, picking up a few items, including toothpaste and a couple of frying pans, as others boarded up the building's shattered windows.

Ruslan broke down when asked how his family was coping with losing Artem.

“I can’t believe he is gone,” he cried.