Casso was shot in September 1986. Gotti was in prison at the time so I think Angelo did it On his own. Gotti May have known about it I’m not sure. But Angelo was very impulsive and when Casso insulted him He wanted to put a hit on him. In October 86 Casso used his Mafia Cops to Abduct and torture Jimmy Hydell who gave up the names. Gotti got out of jail in March 1987 and desperately made peace with Casso. I guess Casso decided to wait a few year but in 1990 he continued his revenge by killing Gotti loyalist Ed Lino without any retaliation