for a moment i thought he didn't, but i think he did. The only way i can see this going down, is....i think he had some deep seeded issues. I think he might have formed a little crush on lauren because she was nice to him and didn't exclude (which is much different than including.) i think he felt a connection with her because he had been going into her apartment for a couple of months, if not years, and thought from the little clues and signs that he saw that they could be together. He might have had some sort of fantasy that if she would just break up with "that guy" in atlanta then she would see that they would be perfect together. I think maybe the last couple of times he went in, she might have suspected him as the one going in and wrote an email stating this. She might have expressed fear of him. I think he read it and it enraged him because he had this "connection" with her in his mind and he snapped. I think he probably had some big hatred/jealousy and a sense of superiority over the "good ole boys" in law school that the girls fawned over. He went into their apartments and took tabs on their condom usage. He probably took their last one or two condoms as a little joke thinking that they would get someone pregnant or an std in the heat of the moment and that would be just deserts for their careless behavior.
Lauren had been working for the underdogs of the world but was dating a high dollar atty who was nothing more than the antithesis of what he thought an attorney should be and what he probably thought she was. I think he probably got a sick satisfaction that the atty boyfriend didn't report her missing and was out of the state. The boyfriend's lack of response was gratifying because it proved his theory that he wasn't in love with her the way he was.