I also wonder about the five witnesses recently called by the prosecution (and apparently vetted by the Judge in a closed hearing - but BK was almost certainly there. Actually, apparently it was 7 people from PA. The article below says that one of them (who must have talked to the press) remembers yelling and violent acting by BK:
It appears that the young prof who wrote his LoR for grad school was among them. One of the odd things said in that article is that BK never threw a bunch in the boxing class (his dad was taking it? he just tagged along for "something to do" as if he was being babysat? The instructor says he had no "fighting skills."
In psychoanalytic theory, one would then ponder whether buying a knife was a compensatory mechanism after all other attempts to be something like a soldier or a policeman had failed. I would think this indicates a profound need to be in control of others - to be "above" them or, even, licensed to use violence as a way of channeling the "crazy thoughts" he admits to in his adolescent writings.
I do wonder if his father, in particular, suspected what had happened (even just a little) when BK came home from Washington to stay.
IMO