Guy pretending to go to my college?

I got to college in the summer before my freshman year to participate in some summer program that let you get a head start on some classes. one night my friends and i got dinner with this guy, a friend of mine had met him at our school's admitted students weekend but he'd chosen to go to another nearby school. cool, whatever. he and my friend clearly get along well, everyone jokes about them being gay and whatnot because they end up basically separating into their own conversation.

anyway, at the beginning of the school year, that same friend and i run into him right before he's apparently about to go to san francisco to work on some ai startup on a gap semester/year/something i forgot. the vibes are weird from my friend , all the closeness from before seems gone and, when the guy leaves, my friend reveals he found out that the guy didn't actually get admitted to our college or the one he supposedly goes to. "ai startup" is also likely bull, hes probably just some bored kid from the area who knows how to mess with people.

i thought id never see him again but currently i am typing this from my dorm room because he has recently started hanging out on my floor's lounge and its freaking me out. I support trolling dumb college kids but he talks with such a serial killer inflection, my friend and i ran into him and he kept telling my friend to text him back. he carries himself like wannabe mark zuckerberg (which is lots of people at my school tbf but its creepier when you factor in the serial killer mannerisms) and is currently trying to turn another friend and i's joke betting system into a cryptocurrency.

I dont know who he is or why hes here, he showed me a fake school id with the name of some kid from my floor that looks like him on it that he uses to get in the buildings, im assuming he has one for the school he claims to go to as well. he also (probably) lies about having lived in like every coutnry in europe. Idk id think it was funny if it didnt make me feel like someone from my floor was going to end up on a true crime podcast. am i overreacting rsp is this guy just bored or is he going to serial k sorry serial unalive someone

quick edit: just went on his instagram and he has no school in his bio and a bunch of tagged posts at a random california university, is this guy a serial grifter i feel insane