I agree with this. I am prepared to forgive, and to have a calm, quiet, sincere conversation with the guilty, urging him to seek eternal peace before it is too late.
Then, as the lawful arm of the impersonal state, serving justice, I am prepared to pull the trigger or flip the switch on the guy and not feel a second of regret.
Blood must pay for blood is the oldest law in human history. We do not do well to forget that this has been a universal human value until recently...right about when our society began to collapse. Public and shocking? Even better. Those who watch the horror of the moment of death for the evildoer do not soon forget that moment. That image in their memory would serve as quite an effective deterrent.
For those malfunctioning enough to be suicidally homicidal, well, I think we should never have abandoned the formal institutionalization process for the mentally ill. Releasing them to the public with instructions to routinely take their medication is asinine, and the vast majority of violent mentally ill offenders I have ever dealt with were not first-timers; they were known and had been repeatedly allowed back into society.