Guess they thought he wasn't quick enough.
Protect and Serve, baby!
Everybody is on edge today, it seems. So far, local polizei do get a lot of leeway; if they had wanted to call in negotiators they probably could have. But this might have been seen as threat-to-be-neutralized. A general cheapening of the concept of one’s fellow man’s life may be partly to blame here. Both in any threats the veteran made and the way the officers reacted.
Look at it from the police POV: They didn’t have a lot of time to reason or negotiate, what with time running out on the doughnut clearance sale two blocks away.