Hopefully, they found some evidence transferred from the killer, around the victim(s) that struggled.
In my opinion, this is going to be a guy that hates women. Men that abuse, mistreat, beat and hurt women are cowards. They choose to prey on the weaker sex, because they are bullies.They don’t usually start off with murder. They work up to it.
I believe the boyfriend was collateral damage. He was in the wrong place at the wrong time. I believe that the killer would have chosen another house if he had any idea he would encounter a male. I would venture to say that he probably didn’t expect to find four females present. He probably had hoped for one or two.
I don’t think the killer is a student. I don’t believe any roommates or ex boyfriends are involved. I say that because those types have certainly been interviewed by now. They would have cracked. College students, from the suburbs, aren’t able to withstand an hours long interview, with a hardcore, tough as nails homicide investigator, and maintain composure.
Street wise, career criminals, that live by the law of the jungle, play tough and lawyer up, when an attempt to get an interview is made. Experience has taught them this. They’ve been handled by law enforcement, previously. You don’t find those types living in a student housing area. They are across town, in the bad neighborhoods.
The longer this goes on, the more I lean towards a serial killer. Maybe an up and coming serial killer.