If Tony Mirra was about to become a co-operating government witness then I'm the king of Siam!!!!!!
I firmly believe Mirra and Napalitano were both whacked because of Donnie Brasco.
It was Mirra who first introduced him to the Bonanno's and Napolitano was Brasco's Capo.
Mirra and Lefty had lengthy sit-downs over who "owned" Brasco - everyone knew this.
Brasco being revealed as an FBI man signed their death warrants.

No way would Napolitano have moved on the family without seeking Gambino and Genovese approval.
Look at the Philidelphia family and the wheelings and dealings and double crossings that went on over their leadership just prior to 1981.
I do however believe Massino over Bonventre's death.
That guy was a cocky arrogant bastard who was way above his station - I can believe the story about him Disrespecting Rusty.
The only one of the 3 that I have any little sympathy for is Napolitano.
The world was well rid of Bonventre and Mirra