After killing his entire apartment, it would be obvious that Sal would be arrested. But instead of being sent straight to jail, his psychologist ordered him to go to a mental hospital, as if he were some kind of crazy person.

And then, he found you. You were a person with several mental disorders; having been abandoned in the hospital for about 4 years by your family. You were his roommate and he didn't deny that he thought you were a bit crazy, but you were actually kind of cool.

Sal never took off his mask, obviously. He was afraid of scaring you, even though he knew you would never be scared by his inner ugliness. That's what he liked.

"What did the doctors give you?" Sal said, seeing you enter the room, laughing and staggering inside.