The gun is mailed back to him neatly. That shows him it's not Jim's idea, because if you're Jim Moriarty, you send a gun wrapped in blood and guts and a soggy bag that should never have got past any type of postal security. There is no name, but a simple message, on fine paper, taped to the gun.
He's dead, Sebastian. Move on.
Three years of waiting, all for nothing. He screws up the paper, and takes a large chug of the green liquid beside him. He doesn't know what it is. He's past caring. Because Jim is dead, he's no longer wanted as a sniper, and he can't remember anything past the last five minutes.
He doesn't know quite what to live for anymore.