There are no clear circumstances before the crime that implicate the officer.
Any actions after the crime, do not appear to show that he meant to do the act, in fact, the actions and testimony of witnesses, confirm that he didn't mean to do the shooting.
He should walk...>LEGALLY, but should resign from any future law enforcement job.
Oh, and there will be a riot unless he is taken out back and lynched immediately after trial, because nothing will satisfy the racists marxists in the Bay Area.