If it is determined that the guy was mentally ill or whatever he will not be tried. Instead, the case will be dismissed and (hopefully) he wont even get a criminal record. The legal term is "diminished responsibility" i.e at the time he wasn't responsible for his actions owing to his condition.
No one on the forum should be abusing him, calling him a Knob or whatever. He is sick, mental illness is no different to someone with another type of disease.