IMO, of what we can observe now, BK is a pretty regular guy. He was a PhD student, TA, well groomed, evidently raised no suspicions among colleagues, students, neighbors, receptionists, medical providers, even his father in the days after a horrible crime. He is reportedly a cooperative prisoner. I think there is a tendency to dig for some reason why this seemingly normal person who committed an awful crime is not normal so we can spot the next criminal, but I don't know if we really can. The last case I followed closely was Mollie Tibbetts, and her killer was also evidently a normal guy - hard worker, decent father, etc. Nobody suspected anything. IMO, this is what is scariest.