This reminds me, I want to try to read The Last Circle again. I say "try to read" because....whooo boy, that is one messed-up book. It's entertaining, but it goes off on about a million tangents about Casolero and the tons of stuff he was looking into at the time of his death. If the author had only focused on the INSLAW case Casolero started with the book would have been half its length but probably just as entertaining, considering the colorful cast of characters involved.
And if I'm a hitman and I get hold of my victim's gun, darn right I am using that. The police can only trace that gun back to the victim, giving them no clues to my identity. Plus I can drop the gun next to the victim and it raises the possibility of suicide.
If you get cheri seymour's book it explains most of it- I'm sure you can find it cheap somewhere but here's a link to it on Amazon- The Last Circle: Danny Casolaro's Investigation into the Octopus and the PROMIS Software Scandal https://www.amazon.com/dp/1936296004/ref=cm_sw_r_cp_apa_i_O9TjCbZDMVJV8
https://en.m.wikipedia.org/wiki/Danny_Casolaro
https://en.m.wikipedia.org/wiki/PROMIS_(software)
The Last Circle: Danny Casolaro's Investigation into the Octopus and the PROMIS Software Scandal https://www.amazon.com/dp/1936296004/ref=cm_sw_r_awdo_E1JK9QV4XVZ8MXYXBXWN