So what I picked up from everything is that he’s a beta trying to join an Alpha only frat, and he’s pretending to be an alpha to get in. It seems he wants to get in because his family is well off (? Perfume company) and he’s trying to build connections or earn a name for himself (from the convo he had in the br w/ Brett). Nathan (the one who got shot) seems to be a typical asshole alpha that is doing frat initiation rituals, and he’s just being an extra asshole to Rex (the shooter) cuz he’s a beta.
I don’t think there is a 100% certain reason why he was targeting Brett yet! From what I could tell, he probably thinks Brett is part of the “lead” alpha gang and maybe just assumes he was in on a lot of the crap….but in the beginning, Brett IMMMEDIATELY spoke up about the hazing pics he saw in Nathan’s phone, and was like. “I thought we weren’t doing that anymore?” So he’s definitely not supporting hazing. He also really tried to give Rex good advice in the bathroom at the charity event. But Rex was so spiteful he didn’t even want to listen. So for now basically Rex is also just someone who’s been bullied to the point where he’s lost his marbles.
I didn't understand certain parts about Rex, particularly why he is being mistreated by others (and who those "others" are) and whether or why he specifically targets the blond-haired guy.