CNN said it could not independently verify the authenticity of the audio. The man's attorney, Lopa Blumenthal, said that her client discussed the tape with the FBI. The FBI has yet to comment on whether it questioned the man who made the recording.
"He heard loud noises and at the time he didn't even realize the import of what he was hearing until afterwards," Blumenthal told CNN's Don Lemon. "It just happened to have captured 12 seconds of what transpired outside of his building."
On the audio, a man can be heard video-chatting a friend while shots ring out in the background. After a pause in the gunfire, more shots can be heard.
A forensic audio expert told the network that he detected a cluster of six gunshots followed by four more after the pause on the recording. A private autopsy ordered by Brown's family found last week that the unarmed teen had been shot at least six times, including twice in the head.
Watch the CNN segment below: