If you failed to steal something or attacked but did not kill him in the Core City church, he will still be present in the Institute later, and will be hostile (which I suppose is intentional). What's not intentional is that he appears in the same state when you left (with unexpired status effects and missing health). For example, he somehow made it back to the Institute as an icicle:
Also, all tchortists turn hostile when you exit the lecture hall, even if he didn't see you.
