Thinking about this over coffee as well. I fear we may be falling further into a reductionist mode of thinking that killing perpetrators is an appropriate answer to violent crime. Jeffrey Fagan, professor of Law and Public Health at Columbia University points out (in 2006) the lack of validity or reliability of evidence that would support such thinking:
“There is no reliable, scientifically sound evidence that pits execution against a robust set of competing explanations to identify whether it can exert a deterrent effect that is uniquely and sufficiently powerful to overwhelm these consistent and recurring epidemic patterns. These flaws and omissions in a body of scientific evidence render it unreliable as a basis for law or policy that generate life-and-death decisions. To accept it uncritically invites errors that have the most severe human costs.” (https://deathpenaltyinfo.org/FaganDeterrence.pdf)
I happen to know an expert witness MD (in anesthesiology) from a prominent US hospital that regularly is called upon to comment on the mis-administration of one form of capital punishment, lethal injections. I would much rather see our government and institutions focused on the root causes of why and how such violence happens, and then to propose and create mechanisms for mitigating those causes.