From my perspective, this appears to be an "inside job." This isn't the actions of an indiscrimate hater. He chose the YWAM facility and then chose New Life church. They are connected (at least tangentially). If he wanted to kill Christians in general, there would seem to be other ways to accomplish that. I will bet that he's received some imaginary or real insult from YWAM and/or staffers from the church and acted on it.
I wonder if he was homosexual.
Strict cold fathering can be a huge environmental factor toward setting that up and then add in strict harsh Christian stuff . . . a real good method to produce fierce rebellion.
DISCIPLINE WITHOUT BONDED HEALTHY AFFECTIONATE EMOTIONAL LOVE
RESULTS IN REBELLION virtually all the time.