In the frigid basement of the Mariupol theatre, she stood in just her bathrobe, covered in white plaster dust blown loose by the explosion. Her husband yanked her out the door and pleaded with her to close her eyes.

Oksana Syomina couldn’t help herself – she looked. She still wishes she hadn’t done it. Bodies, including those of children, were strewn over the scene. A small girl was motionless on the floor near the main exit.

To get out of the structure that had functioned as the primary bomb shelter for the Ukrainian city for more than a week, Syomina had to trample on the dead. Those who were injured yelled, as did those who were looking for loved ones. Syomina, her husband, and about 30 other people rushed blindly toward the sea and up the shore for over five miles (eight kilometres), the theatre in ruins behind them.

“Everyone is still under the rubble because the rubble is still there — no one dug them up,” Syomina lamented, her eyes welling up with tears. “This is a massive graveyard.”

Among the atrocities of the war in Ukraine, the Russian bombardment of the Donetsk Academic Regional Drama Theater in Mariupol on March 16 stands out as the single worst attack against civilians known to date. According to an examination by the Associated Press, the attack was significantly deadlier than initially thought, with close to 600 people killed both inside and outside the building. That’s nearly double the number of people who have died so far, and many survivors believe the figure is far higher.

The AP research used the recollections of 23 survivors, rescuers, and those who were intimately familiar with the theater’s new existence as a bomb shelter to recreate what happened inside on that fateful day.