Let me reiterate: it's been proven nothing else will prevent that person from killing innocents. You send them to prison and they escape. You put them throuh rehab and they relapse. You put them on trial and they walk through intimidation of witnesses or corruption of the judicial process. Mundane authorities consistantly prove incapable of restraing this individual or protecting others from them.
If you've taken up the spandex, you've already tacitly admitted that the system is broken and you have taken upon yourself the moral and ethical responsibility of cleaning up the mess.