Massacre, manhunt and mourning: How Russia's deadliest attack in years unfolded over the weekend

The auditorium at Crocus City Hall was about three-quarters full, with the crowd waiting to see Picnic, a band popular since the Soviet days of the early 1980s. But the concert was sold out in the 6,200-seat hall, so some of the audience was still likely getting food or were shedding their heavy coats in the cloakroom.

It was 7-10 minutes before the start of the show, scheduled for 8 p.m., said concertgoer Dave Primov.

Then came the popping sounds.

“Initially I thought: fireworks or something like that…” Primov told The Associated Press. “I looked at my colleague, and he also said: ‘Fireworks, probably.’”

But it wasn’t pyrotechnics. At least four khaki-clad men with automatic weapons were in the building, firing incessantly. Then they set the concert hall on fire.

It was the start of the deadliest attack on soil in years called “a bloody, barbaric terrorist act.” Although he sought to tie to it, an affiliate of the Islamic State group claimed responsibility — which U.S. intelligence officials confirmed. Kyiv denied any involvement. Four suspects were arrested in Russia's Bryansk region.