Sorry to hear for your loss.
It is sad that in cases like these, the real story will never come out and we will never know if he really was following the girls or they were just paranoid. I had a friend killed about this time last year. He was at some friends house watching TV in their living room while one guy was at the gym and the other was in his room. The door got kicked in, my friend turned to get out of the room and was shot in the back of the head. So far no leads a year later and I think its pretty much become a dead case and of coarse the cops assumed, could of 21 yr olds, probably drug related crime.