Okay, this is simple. He kissed you. This is what is termed as a 'move', a 'pass', it is an attempt to initiate either sexual intercourse or some form of romantic attachment with you. You do not have to judge or try to interpret his actions, they seem clear enough.
Do you want to have a liaison of some sort with him. If yes, then return his kiss. If no, then tell him his advances are not welcome.
No need to ascribe some kind of mental breakdown to him, this is all incredibly simple (if juvenile).