Yeah, pretty much what Cold and Writer said... Marten broke up with Dora about twelve hours ago. He's spent the majority of that time locked alone in his room.
He looks like utter crap, if that helps. And he could indeed be losing his shit. But we haven't actually seen how he's coping with it, other than hints that he's not handling it very well at all. Like I said before, and like others have said too, Marten might indeed be about to snap... but it hasn't even been a full day yet. Let the breakup sink in. And then, maybe, something can trigger him. I'm guessing Marten will manage to control himself until something pushes him over the edge. Then, though, you might wanna stand back.