Just got all the endings, and wanted to say I really enjoyed figuring out who the killers were. The game doesn't hold your hand too much, but there's some nice telltale clues. I'm interested to hear how other people reached the right answer.

SOREN: He was my first guess. He has a few creepy moments throughout the game, and clearly becomes upset when he finds out about Adam and Evander dating... Shortly followed by Starface targetting Evander. I also noticed that he specifically tells Adam to get far away from Timmy's apartment, presumably to make cleaning up the body easier.

JON: Easy, in the Dead End ending, Starface talks with a country drawl. That and his general hatred of Adam at the awards show.

ABZI: The Violent and Gutless endings make this one obvious, although I had some trouble actually getting to those endings. Notably, he was also being a mentor to Jon, tying them together.

JOHN: Didn't make the connection right away, but should have realised if Jon was involved, so was John. Also occurred to me that he's probably the one who spiked Adam's drink at the awards show.

HUNTER: I'll be honest, I only picked Hunter after I got the first three and then realised the killers are the five on the game's title screen; Soren plus all the studio exclusives. He has some creepy survival of the fittest thinking. He's presumably also the one who attacks Adam at the awards ceremony, choosing to use a hammer. Explains why he didn't attend the award show (Chuck gets a free pass because he has no real connection the others, and is the only performer who isn't super intense in some way).