I never bought into the story of Johnson being hired by the mob to kill Columbo. He had press credentials that were close to impossible to get, and Greg Scarpa on the scene working with the FBI.
Are you saying the government did it? Genuinely concerned here. I've always been interested in the Colombo shooting, who was behind it.
Check out Colombo: The Unsolved Murder by Don Capria and Anthony Colombo. I'm not convinced it was the government who killed him, but they dispel the myth it was Gallo.
It was a very good book, unfortunately it did not get anywhere near the amount of attention it deserved. Anthony Columbo seemed very crediblle, he would not have been so kind in his words about Carlo Gambino if Gambino had really been behind his father's assassination. There are other books and reports of FBI covert operations in the time period. A few reports are available online.
