Someone rushed in and made a mess here ~ you know that, right?
I know that is your spin on the story. I think you're full of carp. You wanted to know what their probable cause was, it well may have been the dog. A dog alerting on a person is probable cause in all 50 states.
It was the deceased that refused to show empty hands and who fired first. Seems to me he's the one that made a mess. I wonder what the blood screens will show, cause I'm guessing the stupid little git was seriously messed up. Of course maybe he was just congenitally stupid.