Chances are that whomever had to go to prison didn't get there by attacking a police officer, but some other person who was unarmed. Just because a police officer catches and a court convicts the perp doesn't mean the perp, once released, will only go after the police henceforth. The perp will continue to go after unarmed people - yes, the easy targets.
The answer to this kind of crime is to keep such perps locked up, institutionalized, under full time guardianship, or execute them, and the people should be armed to thwart these perps in the first place.
If those people in government would abide the Constitution and all its amendments, we wouldn't be having this discussion in the first place.
Woody
"Give a man a policeman and (maybe) protect him for a day; give him a gun and protect him for life." Elzorro