My opinions are that vigilantes should be allowed to stop crime but not allowed to kill unless they have no choice. Like if they criminal has the mayor or some victim as a shield and they will kill they victim they would only have two choices shoot the victim and risk their life or the can shoot the criminal in they head to stop them from kill the victim.
Vigilante justice is stage one law. There is a reason that we are now at stage 4 law, because we don't live in a third world country we have a justice system and if you have enough evidence to prove that a crime was committed then that person will be punished as per the law. Having strangers being able to attack a person violates so many of our rights.