Prosecutors in Arkansas say Andrew James McGann left a hiking trail at a state park a bloody mess after stabbing a couple to death ... and folks saw him leaving the scene with blood on his face. In new legal docs,

Clinton David Brin and his wife, Cristen Amanda Brink, were "fatally attacked" while out hiking with their two daughters at Devil's Den State Park, police said.

The teacher arrested and charged with fatally stabbing a couple hiking with two of their children in an Arkansas state park has roots in the Chicago area.