A newly surfaced audio recording allegedly captures the exact moment that unarmed teen Michael Brown was shot and killed by Ferguson police officer Darren Wilson.

According to an attorney for an unidentified man who lives in an apartment building near the site of the shooting, the recording captures as many as 11 shots fired in the Aug. 9 incident.

The audio, which was played on CNN Monday night, could not immediately be verified by The Washington Post. But a burst of gunfire can be heard (six shots), followed by a pause, and then several more shots (at least four).

“He was in his apartment, he was talking to a friend on a video chat, he heard loud noises and at the moment — at the time he didn’t realize the import of what he was hearing until afterwards,” the man’s lawyer, Lopa Blumenthal, said in an interview with CNN’s Don Lemon. “It just happened to capture 12 seconds of what transpired outside of his building.”

According to Blumenthal, FBI agents came to her office on Monday to interview the man about the recording.

The 12 second-audio clip is the only using a cell-phone app that only records short excerpts of a video conversation. It captured nothing before the shots began and nothing after. The man, who would like to remain anonymous, has asked that the accompanying video not be shown, Blumenthal said in an interview with The Post.

She first learned of the audio clip through the man’s roommate, who is a former client, and she urged him to share it with authorities.

“He was there when the event happened,” Blumenthal said, adding that he initially assumed the noise was fireworks not gunshots. “He is a very private person and he his not seeking publicity of any kind whatsoever. He was even unaware that this tape was relevant to anyone.”

Neither Ferguson nor St. Louis County police have contacted the man or Blumenthal about the video. After interviewing him on Monday, she said the FBI indicated that they planned to speak with him again on Tuesday.

Autopsy reports conducted by St. Louis County and by the Brown family found that Brown had been shot at least six times, including twice in the head.

[This post has been updated.]