short version:
there was a struggle with two officers, suspect took taser and broke free, aimed taser at police while running away
got shot
No excuse to shoot unarmed man running away. The taser was discharged, missed (maybe out of range) and not a deadly weapon in any case. Cops shot accidentally or lacked proper training. Court can sort that out.
This video shows the guy fired the taser at the police while he was running, it looks like the taser hit the one cop... starting at 28:32
https://www.youtube.com/watch?time_continue=2400&v=MawQYNNIoZ0&feature=emb_logo