Only after public outcry. What do you think would have happened if there weren't anyone watching?

I think they got him confused with the officers that unloaded 20 rounds in a no-knock warrant, killing an EMT not involved in the investigation, and resulting in no evidence

In that rare instance charges were filed, but there is yet to be a conviction. There is a vast system in place to protect police officers in these situations, up to and including federal law.