If it's a mole, dig into the tunnel, set a mole trap(hook some bailing wire or something to it leading back out to land, in case it tries to bail into its tunnel after hooked) You don't even need to bait it, just put it in the tunnel and "cover" it back up.
Contrary to popular opinion, I think moles are rather solitary critters, and generally don't frequent other moles' tunnel systems, so after you snagged the fella, leave his ass to rot in the tunnel. It'll keep others from taking it over for their own.