EDGERTON, Wis. (AP) — Austin Schumacher parked his unmarked squad truck and watched pheasant hunters work their way into the woods under the overcast, late-fall sky. The rookie Department of Natural Resources warden had just popped the lid of his salad container when the radio squawked: a 13-year-old boy, missing.

The boy had run away from Edgerton Middle School after a dispute with his teachers — he swore at them before he ducked out of the school and headed into the swamp across the street. Principal Clark Bretthauser tried to follow, but lost him in the mucky underbrush.

The boy was clad on...