Jack Lupino is an Underboss of the Punchinello Crime Family in Max Payne. He was mentioned several times by Mafia thugs, especially by Vinnie Gognitti that Jack was going crazy, and indeed he was. (Vinnie even stated in a letter that he blew a thug's brains out because he wanted to see what his brains looked like on the wall). Jack is addicted to Valkyr and is clearly insane, worshipping devils and believing that he is a wolf and a messenger of Hell.
He is only seen in one chapter throughout the whole game and he was killed by Max shortly after. Max even shot him multiple times after he died, just to make sure he was 100% dead.
Jack is surrounded by cultists wielding shotguns, molotov cocktails, and ingrams. Keep moving and keep firing with a cool head. Despite his somewhat intimidating demeanor, Jack himself is probably the easiest boss in the game; he uses a Sawed-off shotgun and after he fires his first two shots he is completely open to any sort of attack. It is possible to even bludgeon him to death easily with a baseball bat. Every time he is hit while he is reloading, he is forced to start his reloading animation over again. To sum it up, kill his henchmen, dodge his first two shots, then finish him off with the weapon of choice.