James Files was the actual shooter (one of several and the one who fired the kill shot). Look on YouTube for the interviews with him and see if you aren’t convinced.
It was a mob/CIA hit.
Showtime made a bio flick Bonanno about Joseph Bonanno. He was in his 90s and retired to Arizona with the approval of the commission. He set his boys up as owners of Sacramento trucking Company legit business.
After the 2 hr 50 minute movie, they interviewed him. he said the mafia put out the hit because of the Kennedy brothers prosecuting them. He did say a shooter was in the sewer opening, but I think that part has been debunked.
Giancana was godfather in Chicago and he had LA and Dallas under this authority. That would have made a connection to Marcelo who has a lot of circumstantial evidence against him with meetings and RFK having his men snatch him off the street and dumping him in Guatemala after they lost the hearing to deport him.
Also, i have read that giancana was getting very upset and he told Johnny Roselli to go to Hyannisport and talk to Joe kennedy and have him remind his boys that the mob carried WV with the UMW and that defeated humprrey in the primaries and influenced votes in Chicago.
Roselli and another guy went and Joe said at christmas when they are here I will take to them. He had a major stroke before that and is is very likely that talk never occurred because he was incapacitated.
My money is on LBJ or the Mafia. LBJ had the most to gain and the hatred was well known. The mob didn’t usually hit public figures at high levels but the Kennedys were very strongly pursuing them.