The 46-year-old man, who only wanted to provide his first name, David, to reporters, says he was at the Comptoir Voltaire café near the Stade de France on the night of the attacks. Amateur video captured the chaotic scene after an explosion rocked the building.

David was performing CPR on one man whom he described as having a large hole in his side. When he removed the injured man’s shirt, David saw wires attached to the injured man’s body, and knew who he was.

A suicide bomber.

Before seeing the wires, David had believed the incident was a gas explosion, not a terrorist attack. When he told authorities about his findings, the building was immediately evacuated.

The injured man was later identified as Brahim Abdeslam, one of the Paris attackers. The bomb had only partially detonated, and while Abdeslam died from his injuries, no one else was killed at the café.

As for David, he says he relives the moment over and over. He realizes how lucky he was that the bomb did not completely detonate, and how he unknowingly had put his life in danger by performing CPR. Reuters reports that David has not been able to go into restaurants or cafes since the attacks.