Mafia Movie I can't remember?

All I remember is that at the beginning, a mother and son are
separated, he goes off and turns into this super evil hitman/mafia
murderer dude guy, and at the end they have sex and then she ends up
killing him, I think because she finds out that he's this assassin,
and then he finds this chain around his neck that she gave to him at
birth and before dying she asks him who gave it to him and he yells
out "My mother!" in italian just before dying...

Any ideas?