Shooting him maybe, they burned the house intentionally. Which is murder.
I understand your revulsion, but in point of fact the law does not make a distinction between types of deadly force. If it is legally acceptable to kill, the means by which it is accomplished are not an issue. Citizens have been killed by police cars, police flashlights, and for all I know police dogs. How the killing was carried out didn’t matter if the facts established that the officer was legally justified.