Justice is just an illusion. No one ever gets back what they once lost. It's a matter of believing that it is, in some way, getting even with those who is thought to be responsible. I don't know any of these folks but as for myself I would have to be mentally deranged to even think of such an act.
If someone murdered my daughter, first I would want to know what drove that person to do such horrible crime. Second, I would want to know that someone else would not fall victim to the same perpetrator. Third, I would want to know what can be done for that person so they would not be driven to commit this insane act again. If that means to be locked away for life then, so be it.
I would be incensed, but to seek revenge or demand justice that in some way will cause additional mental or physical harm toward the attacker will not bring back my daughter and will only result in poisoning the soul of those insisting on such action.
I don’t believe in “punishment” because it demands a change in behavior for all the wrong reasons, therefore, it is usually not successful in resolving the destructive conduct.
As much advancements that have been made in psychiatry and psychology there are too many other alternatives to remedy these problems, but we as a society, still seek this false since of justice. Oh well, maybe some day we will evolve beyond this misconception.