Award-winning photographer Patrick Zachmann of Magnum Photos was on Republique Square in the center of Paris when he saw police cars and fire trucks speed by. “I knew something was strange,” he tells TIME in an interview. “I immediately thought of a terrorist attack.”

In a career spanning four decades, Zachmann has covered everything from the 1989 Tiananmen Square showdown to the violent Neapolitan crime world. So when he heard the sirens echoing across Paris’ quiet streets, he instinctively followed a police car down Boulevard Voltaire toward the Bataclan concert venue – where at least 89 people are now believed to have lost their lives in the carnage.

Facing the corner of Passage Saint-Pierre Amelot, where the Bataclan is situated, Zachmann hid behind an unmarked police car, took his iPhone out, and started photographing and filming as police attempted to end Friday night’s siege. He shared the footage with TIME, which can be seen above.

“I heard the shootings from a Kalashnikov,” he says. “In the videos, you can actually see the sparks [from the bullets hitting the ground].”

Zachmann could sense the fear and nerves of the police officers around him, he says. “It was panic. You felt that it was not under control, that they didn’t know what was going on, from where exactly [the terrorists were] shooting.”

At one point, a police officer joined Zachmann behind the parked car. Holding a pistol, the officer advised the photographer to move slightly to the left to use the car’s wheels as protection from potential strayed bullets.

“He seemed tensed, very concentrated,” Zachmann says. “I could feel his fear. I could feel that maybe he was not used to this situation. They are trained, but maybe it was the first time he was on [such] a scene. But there was a kind of complicity [between the two of us]. He could have asked me to leave, but he let me [stay] there.”

The city has already started to mourn, lighting candles on Republique Square in scenes that are reminiscent of how Paris came together after the January attacks. “But [you can’t] compare,” says Zachmann. “During the Charlie Hebdo attacks, it was such a shock for the French people… Today, we’re not in this mood. It’s after Charlie. We know that we are in a war. Far away, in Syria, but also inside. Even in France, we are in a war.”

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Write to Francesca Trianni at francesca.trianni@time.com.