I like your idea of getting some military snipers to bring down these guys (or guy). That does sound like a very sensible solution. However, I don't think that is going to happen.
A couple of things:
1. This guy (or guys) will be bagged by sheer chance. Snipers are trained to be patient people. That's where tracking comes in. Every bit of evidence would have to be provided to the snipers to assist in setting up their firing locations. Good tracking and hunting will help, but in the end, some Marine will have to get real lucky.
2. The sniper, or snipers, has to make a mistake sometime. That's when we'll bag them.
Finally, I cannot emphasize enough that I believe this individual to be a professional or a group of professionals. LEO's do not faze him or them. Only when he or they know they are being hunted will they start to trip up.
Right now, he or they are laughing at the LEO's.
Be Seeing You,
Chris