My personal theory that he was essentially between being a police informant and being involved with cigarette/liquor/weapon smuggling across the border.

To me it’s very likely he was an informant, he was able to get away with shit (his open secret police car, performing a citizen’s arrest on a pair of cops) that would get most people in trouble and there was that large cash withdrawal shortly before the shooting that was more than suspicious. He had close ties to both biker gangs like the hells Angels and law enforcement. Hell, one of his targets that day was a couple of prison guards he knew, he spent something like an hour and a half at their property and burned it to the ground as he left.