Buddhists have been well documented to perpetrate violence on Christians. Same with Hindus and Muslims.
He may have used Buddhism as a cover and was not one to begin with.
Over a million Buddhists have been murdered by the communist Chinese since their invasion of Tibet in 1949. That they may be resisting Muslim hedgemony in Myanmar and other such countries is not surprising. Violence against Christians is minimal.
What effect do you think paranoid schizophrenia and auditory hallucinations had upon the shooter's actions?
I can only think of one group that fits into your statement that is the Liberation Tigers of Tamil Eelam. They like to target Hindu’s mostly
Navy Yard murderer Aaron Alexis created webpage with name “Mohammed Salem”
http://www.freerepublic.com/focus/f-news/3068741/posts