Hang on............. So in the context of the conversation they were having, I think that boasting that he could kill faster than an animal, is a little bit of a red flag.
What reason would he have to implicate himself in the case of MP or MM by bragging?
Perhaps he just likes very dark humor or wants to be seen as a 'hard man' peado - Or get's a kick out of people double guessing him, thinking he's smarter than everyone else.
I'd imagine friends may have always seen him as a 'A' hole and probably brushed off his boasts and brags over the years, but then the bigger picture started to form and this is what the BKA has now.
Just like he teases the BKA with his drawings and letters, this some kind of game to him. All typical, dangerous. manipulative, narcissistic behavior IMO.
Game's up - hopefully!
MOO - JMO