Howard been not paying dude since the beginning of the movie. Even tho he won there was no reason to believe they would get paid. Plus Howard had the nerves to lock him in that tiny vestibule for an entire basketball game?! Dude was sick of him and just went the robbery murder game route.
I KNEW some shyt was going to do down in those last minutes. There were dark, brooding undertones all throughout the film that told me that there was only one ending for Sandler's character.
I might have to revise my top 10 films of the decade after this. Absolute gem of a movie.