Some context: I'm a soldier in the Portuguese army and there is a 20 year old guy (who I'll call Peter) who might need some help.

Last December we heard that Peter was coming to our base, one of my mates who was also from Peter's base knew him and told us that he was crazy, was always alone and very quiet, and was probably autistic.

He told us of a time where Peter beheaded a bird and another when in the middle of the night he cut 7 pillows and slashed his matress, and how sometimes headless rat corpses would show up.

So January comes and Peter shows up here, initially quite a normal guy, just a bit shy. But as time goes by he starts becoming more secluded, never starts conversations and always avoids other people.
I've heard him punching his locker from my room and I've noticed that he doesn't even shower, he just changes into his pajamas when he's alone and hangs his (dry) towel.

Now this is the really worrisome part, he has cuts in his arm, I've only seen a few on his wrist, but the other people in his room say his left arm is full of scars and recent cuts.

So what should I do? I could report him or maybe just talk to him, but I don't know if that would help, I just know that a guy like him shouldn't be given a rifle with enough ammunition to kill 38 people.