I'd want to hold fire on diagnosing him, especially from an armchair perspective. And his actions appear to be too premeditated and organised to suggest paranoid schizophrenia. Besides, we'd have to assume that all mass murderers are drive by mental illness - I don't particularly hear this bandied around where the perp isn't white. Just sayin'...

The key thing is that whatever his motivation was, this was a horrendous attack. The response of the local community has been incredibly restrained and dignified, and stands in stark contrast with the terrorist's actions.