I'm with you on this.
While that is my first instinct, it would not be the first time that some CI got a few bucks for a fix and the police got bad intel. Plainclothes undercover guys (dressed to blend with the riff-raff) might take on the appearance of a home invasion.
Break down the door, shoot the dog, and it's on. Especially in a stand your ground/castle doctrine State.
If the police did not identify themselves, what could have been a relatively tame bust for some grass and whatever the powder was, turned into a blood bath, quite possibly unnecessarily.
No priors? Lived there 20 years and stayed off the radar?
A little grass, some powder? no cash stash, no heroin, no marketable quantities, no paraphernalia? Two dead and five wounded? Doesn't make sense--not that life always does.
Something doesn't set right, from the accounts given. YMMV