People have patterns. They are creatures of habit. Wait, watch, plan and practice in silence them create and execute a rendezvous with death for this monster. It must be an obsession and must be done alone to be successful but it can be done. It may take years though.
Especially with the sheer numbers involved in this case...
In one season of Dexter, a pedophile makes the mistake of targeting Dex’s girlfriend’s little girl. It was fun watching Dexter stalk and do his serial killer thing on that particular monster.