A Missouri police sniper killed a 2-year-old girl. Why did he take the shot?

It looks to me that he did not identify the target properly, but he fired anyway. When I was in tanks, it was the responsibility of the gunner to tell me if the target was identified which means what kind of target it was and was it friend or foe. He did not have a positive identification of the target and it was ambiguous. He shot without knowing what exactly he was shooting at. Thats how friend fire accidents happen.