From my understanding of the situation, it is a co-ed dorm. If that's anything like what my son lived in at UMass-Amherst, it means there are guys and girls all over the place, all the time, and among them, some who had dated, had broken up, and one or the other was now dating someone else. It's a hothouse of human emotions, and there are going to be what would be considered anywhere else, 'domestic disputes'.
Turns out the shooter probably wasn't the young lady's boyfriend ~ just her stalker ~ as were a whole big bunch of other girls.