For a few confusing moments, the first pops of gunfire, muffled by loud music and a raucous crowd of young people, were mistaken for firecrackers.

The American rock band Eagles of Death Metal, which had already been onstage for an hour, must have included a pyrotechnic flourish to the end of their show, some concert-goers thought.

Then the music stopped, the shrieking began and terrified crowd hit the floor.

Standing in the the back of the venue were at least two young men holding automatic weapons, possibly AK-47s, witnesses reported. Dressed in black and strapped with tan suicide vests, their faces fully exposed, they emptied their guns into the crowd with an eerie deliberateness, mowing people down, calmly reloading, and then continuing to kill.

“They were not moving,” Julien Pearce, a journalist who happened to be in the crowd, told CNN, referring to the gunmen. “They were just standing at the back of the concert room and shooting at us. Like if we were birds.”

Over the next 15 minutes, the Bataclan, — a prized Parisian institution that has hosted luminaries like Edith Piaf, Nick Cave and Lou Reed over the years — was turned into a slaughterhouse, witnesses said.

Authorities said at least 100 people were killed inside the theater.

“It was chaos,” an audience-member told Le Figaro. “I was on the right side of the concert hall in the Bataclan, a song of the Eagles of Death Metal was about to wrap up, when I heard the sounds of explosions, like firecrackers. I saw the singer take off his guitar, I turned around and saw a man with an automatic weapon fire in the air.”

Another witness told France 24 that she heard “loads of shots,” but didn’t realize what was actually happening until the crowd ran towards the exits, according to People.

“That’s when I saw people with blood all over their clothes, and another was shot in the leg.” she said.

“I am very lucky to be alive,” she added.

Some survivors took refuge behind the stage, others hid beneath dead bodies or played dead in hopes of going unnoticed by the gunmen.

Marc Coupis, 57, who was on the far side of the hall when the shooting began, told the Guardian that he got on the ground and ended up pinned against a wall with one man on top of him and another on his side.

The men remained there, expecting death and too scared to move, until police arrived and told them to run.

“It looked like a battlefield, there was blood everywhere, there were bodies everywhere,” he said.

“I saw my last finale unfurl before me, I thought this was the end. I thought I’m finished, I’m finished,” he added. “I was terrified. We must all have thought the same.”

While many witnesses described the gunmen as calm and quiet, a concert-goer who identified herself as Jasime told BFMTV that the shooters revealed their motivation before nearly killing her.

“They said, ‘What you’ve done to Syrians, well now you’re paying for it,’ ” she said. “Lots of bodies fell. I ran into a body. And then I went to the bathroom, and when I came out, there were lots of corpses around me. One guy shot me in the ankle. I’ve never seen as many dead people around me in my entire life. I’m traumatized.”

In one of the more harrowing videos to be released in the hours after the massacre, a woman trying to escape the theater was filmed hanging by one hand from a second-story window, according to the Sydney Morning Herald. The video captured by Daniel Psenny, a journalist at Le Monde, also shows panicked survivors streaming out of an emergency exit and over bodies as they attempt to escape machine gun fire.

The video is chaotic, but the details reveal a web of individual horrors. One bloodied man, his body limp, checks his cell phone as he appears to lay dying in the street. Another man pulls a victim away from the theater by his arms as a trail of blood emerges from the man’s lower body.

One person, who appears to be weeping, cradles another before abandoning the body on the sidewalk, perhaps to save their own life.

Other audience-members emerge from second- and third-story windows, desperately looking for a way down.

“I live on the second floor, and my apartment overlooks the emergency exits from Bataclan,” Psenny told Le Monde. “Everyone was running from all sides, I saw guys on the floor, blood … I understood that there was something serious … Everyone flowed back to the Rue Amelot and Boulevard Voltaire. A woman was clinging to the Bataclan window on the second floor. I thought of the images of September 11.”