Additionally, someone is innocent until proven guilty and that's not the cops job. The cop shot someone not guilty and now people are speculating about the crimes that person could have done to justify it

This is an interesting ethical dilemma which I don't know if there's a clear cut answer. It's a variation of the trolley problem (sort of). I think it depends a lot on the risk assessment being made. I don't know the details of this particular case, but I can think of plenty of examples where a potential future danger should be limited by direct action. I'm happy to provide examples if you're interested in exploring this thought further. I don't know that I have a simple yes/no answer to this dilemma (also why I never became a cop).

Of course it doesn't because that "somebody" isn't someone you know. If that "someone" is your family, what do you suggest he do?