It seems Brooks wrested the taser from the cop.
The taser was active.
The taser was pointed at the cop.
The active taser was shit at the cop.
The question then us: what was the timing vis-a-vis the shooting of Brooks and Brook’s shooting the taser at the cop?
According to the videos it appears that Rolfe fired his pistol after Brooks shot the Taser at the officers. Brooks' shot was the second dart. The Taser was not a threat after that. That is the scenario that the DA laid out during his press conference.