That is a very interesting question. I don't think there is a specific answer. But generally speaking I would assume all murderers would be in a heightened state of emotion or arousal. For psychopaths it might just be a thrill (as one I saw chillingly described it). Despite what people think, many criminals are not inherently bad people. They are just like you and me. The difference is that they have either experienced severe trauma at some stage of their life or exceptional hardship of some kind. For these types of killer, I suspect their state of mind can be described as emotional distress. Either extreme hate, sadness, anxiety, frustration, desperation, loss, self loathing or a combination of all of these could be used to describe what is going through their mind. Perhaps even relief, if only for an instant! It is not surprising that many killers turn out to have some underlying mental illness. In fact their are similarities between people that are suicidal and homicidal. Both are at the end of their tether (psychopaths are a completely different beast). While I agree we need more stringent laws to protect the innocent, that is not going to address the root cause of the problem. We need to be taking mental illness as seriously as we take heart disease, diabetes and cancer. The current economic situation is only going to get worse (lets face it) and mental illness will increase, I promise you. Growth in crime, suicide and homocide will follow with it. People can expect more shootings until we start taking mental health and the underlying causes of mental illness seriously (many of which are economic and involve peoples employment situation).