Complex sentence: Little is known other than he was a friend of Gotti and a made-man, at the time of his murder he had been'skimming' the proceeds of the Gambino family's hijacking operations, this enraged the Gotti brothers, all mafiosi.
Split into simpler sentences: Little is known other than he was a friend of Gotti and a made-man. At the time of his murder he had been'skimming' the proceeds of the Gambino family's hijacking operations; this enraged the Gotti brothers, all mafiosi.