State sanctioned murder won't solve that problem!
It seems to me your main gripe is with the justice system letting these people loose. That is a job for our legislators to solve. Talk to your representatives in both the State and the Federal bodies. Get laws that remove the power from judges to set these people free. They are innocent until proven guilty but they could be locked up until a trial determines guilt. Or did you just want to jerk guilty looking people off the street and put a bullet between their eyes? We make vigilante justice illegal a long time ago and with good reason.
So put money where your mouth is and start working toward changing the system. You're either part of the solution or part of the problem.
I just love cliches.