If all were in bed and likely asleep (according to the coroner), then killing all four only makes sense if all of them were the target. And if all of them were the target, this was almost certainly premeditated, psychopathic, and random. If it would've been perpetrated by an aggrieved ex, a jealous friend, a slighted frat pledge, or someone similar, then a gun probably would've been used and a single target chosen. Stabbing four people to death indicates an obsession with precision and the "thrill" of power and intimacy to me, which is why I feel the suspect is either an established or budding serial killer.
My opinion.
My opinion.