My son is with YWAM in Australia and another fella at his base said his brother had been in Denver with Matt Murray and that Matt had assaulted his brother. So that might have been one reason he was asked to leave. Another person posted recently that YWAM goes the extra mile with folks and it would have taken alot for them to have asked him to leave.
http://www.cnn.com/2007/US/12/10/shooter.youth/index.html
Looks like the problem was that he heard voices, and played some dark rock music in a concert at the mission. Sounds like some kind of mental illness.
I'll buy that. Overall, a wonderful organization and a credit to Christianity.