Borgesi was getting into with Rocco. I do believe he set the whole thing in motion. Dom Grande is who I believe was the actual shooter or part of the team, as he had more easy access then Canalichio, while Nicodemo has an airtight alibi.

"I have this Nightmare. I'm on 5th avenue watching the St. Patrick's Day parade and I have a coronary and nine thousand cops march happily over my body." Chief Sidney Green