Creepo

I'm starting to think my boyfriend's new roommate is a serial killer, or at least someone with severe social phobia.

Silent Boy never speaks to us. When we enter the apartment we can hear him close his bedroom door to avoid us. He has his own bathroom, and keeps food in his room so he doesn't need to leave. Sometimes he's so quiet we don't know he's home. Often, my boyfriend doesn't see him for days. They communicate through notes and checks taped to the doors: "This month's electricity bill is $34.54."

We know he's avoiding us because if Silent Boy comes home while we are already present, he rushes past us and goes into his room without saying hello.

Should I be afraid?