Regolith
Member
I think the 18-year old knew precisely who lived there. I'll wager there was a threat or an ongoing issue, and that's why the boyfriend was there. The aggressor probably had no idea the boyfriend was there, but it sounds as though the boyfriend wasn't in the same room as the girl, given that the aggressor was able to start attacking her, and she had to "immediately alert" him. Sounds like they were expecting that something was going to go down. I'm not saying that's a bad thing... only that there's more to the story.
I think you're reading a bit too much into it.
Sounds more like to me that the intruder had rape on his mind. He saw a young female apparently alone in the apartment, broke in and attempted to attack her. This actually happens far more often than you would think.