I believe the shooter was mentally ill, but that's not something you can always tell just by looking at some one. considering that people have been shot for looking the wrong way at some one when it comes to a conflict like this I'd say it would be safer to err on the side of caution and not put yourself in a situation where your own weapon can be removed and used against you.
I agree, and hopefully most cops would agree, but I still want to leave it to their discretion to use less force rather than bind them to the requirements of a rulebook that can't factor in the context of the situation they're in.