// Had I got hold of the knife I could well have killed her //
Given the circumstances you described, it's unlikely you would have been indicted for murder. More fitting would be a charge lying anywhere between Self Defence and Manslaughter.
With this particular individual, there is a likelihood that he was suffering from a severe mental illness or had been subject to physical and emotional abuse when younger.
Some will say he was the personification of 'pure evil', for there can be no excuse for the slaying of innocent people. I will not subscribe to this view on the basis he took his own life.