People with mental health issues usually are harmless. Bipolar and schizophrenia for example.... most of these people are harmless they wouldn't touch a fly. Same with major depression, anxiety, etc.. I don't know exactly why people commit these acts, it may be connected to mental health but its not the mental health itself.... Hitler for example didn't have a 'mental health issue' he was a psychopath.
I don't know if I got my point across.