Cases like this, we need to differentiate between making choices that are wrong in hindsight and ones that are wrong at the time of their making because they create an unacceptable risk. Only the latter kind of mistake is what we should punish. Not every cop who shoots a 7-year-old girl deserves punishment. It's possible for that to happen without the cop doing anything morally wrong at all in some circumstances, and if they haven't done anything morally wrong, they don't deserve to be punished, no matter the consequences. But look at the facts in this case and it's clear as day this was a choice that was morally unacceptable, and the cops deserve severe punishment for it that reflects the gravity of their culpability.
In NY, by the way, killing someone by shooting at a house you know to be occupied for no justifiable reason is reckless homicide, which is Manslaughter in the 2nd Degree, a grade C felony with no minimum sentence and a maximum sentence of 15 years. Police have a special defense for the use of force while making an arrest, but it does not apply to reckless conduct that injures an innocent party. See NYPL 15.05(3), 125.15(1), 35.30(1)(a), 35.35(2) if you want the details.