Those two categories are not mutually exclusive. I don't think there is any risk of legal action against the police, even if what they did was unconstitutional, imooral, etc. (not saying it was, just saying), because that too carries PR issues.
-- One deputy had already been killed. So the perp was already a known killer. --
Very few known killers are subjected to arson by cop.
Yeah, they usually get shot to death first.