Reports I have read said she had just been dropped off by her new boyfriend. Probably his car was seen leaving the area around the time of the murders made him a “person of interest”, and he was stopped by police.
Greasy hair? Pickup truck? He dropped her off at her dorm at that hour? Sounds like nitwit was stalking her, knew she was sleeping with this guy over night, and got up early to observe her being dropped off! Accuses her of having sex with the guy and kills her!