Why was he shot by police as he was being treated for his injuries? Seems kinda cruel?
Yes, I noticed that as well. I think it was an error by the Israeli writer. From what I heard in a radio report, the perp was shot by police in or near the Chabad facility. My guess is that he was then taken to a hospital for treatment of his injuries, where he was pronounced dead.
I wouldn't like to think of the riots that would be touched off if he were shot by police in the hospital. It would probably be a repeat of Crown Heights c. 1991.