I’ve had a chance to do a little more analysis, and pulled a third recording.
When Crooks fires, there is a shockwave followed by a muzzle blast. The gap varies between 0.21 and 0.22 seconds, averaging 0.215. There’s also a consistent echo of the shockwave at 0.122 seconds. These facts create a fingerprint that allows the identification of his shots on the recording.
The video at the source says there was a burst of five shots, but he didn’t properly identify everything and he’s counting at least one as two shots.
Crooks fired six shots. Counting seconds from his first shot they are at: 0, 0.86, 1.54 seconds in the first grouping. The second grouping they are at: 4.32, 4.58, 5.09. He’s firing at double the rate of the first group. Gets three shots off in 0.77 seconds.
There is a shot between Crooks’ 5th and 6th shots, obviously, not from him. It’s a rifle shot and there’s a different shockwave precedence.
Later, at 5.8 seconds, there’s another shot, from some different source. This is after that second grouping and Crooks has already stopped firing. Then much later there’s a third non-Crooks shot at 15.8 seconds.
There are nine shots on the recording. Crooks fired six of them. My assumption would be that law enforcement fired the other three at Crooks. Probably one of the last two unknown shots killed him.
I expect, when we get a full report, it will say that three people fired back at Crooks. The mere presence of shots that didn’t come from Crooks, in these circumstances, does not imply a second assassin. But we’ll have to wait and see what the investigation produces.