When Dane County Sheriff's Deputy Dave Hafeman entered the 8-by-8-foot passageway leading to the tunnel Friday afternoon, the guard who controls the heavy metal doors on each side had gone home for the weekend.
"This is an area that, again, is secure, and the doors lock behind you as soon as you enter," sheriff's spokeswoman Elise Schaffer said Monday. "And once you're in, you're really at the mercy of the controller to let you in or out."
Hafeman, a 14-year member of the sheriff's department, was not discovered until his wife called police because he never returned from work. Detectives found Hafeman's car parked in the county ramp and traced him to the tunnel.
Schaffer wasn't sure why Hafeman, who was unhurt, had entered the tunnel in the first place.
