Hi Owney welcome to the boards. According to Greg Scarpa's FBIfiles, he told the FBI who he thought killed Jerome Johnson, the guy who shot Colombo. Unfortunately, the name of the suspected killer is redacted. What this means, in my opinion, is that the FBI knows who killed Johnson, but because the person who killed Johnson is still alive (or died recently, the public files are redacted (crossed out).

No one was ever charged with killing Johnson. One of the other knowledgeable posters may have a better guest who the bodyguard is/was.

Here is a link to the Scarpa Files.
http://vault.fbi.gov/gregory-scarpa-sr

You say share my life, and I think share my tequila. And then I think.... no.-Principal Lewis