In "King of the Godfathers," Anthony DeStefano writes that Mirra had been lying low after the Brasco blowup, and Massino got suspicious. Sonny Black definitely was a rival to Massino. So, I suppose, the Brasco fiasco provided an excuse to what both of them.

In "Donnie Brasco" (the book), Joe Pistone writes that before Brasco was withdrawn from his assignment, Mirra and Lefty Guns had a long, contentious sitdown over who "owned" Brasco: Mirra brought him in, but Lefty mentored him. Lefty "won" (if you can call it that)).