A Wisconsin man was found Wednesday living in a bunker along the Milwaukee River.

Geoffrey Graff, 41, was in a 20-foot long bunker built 8 feet below the ground on land owned by Milwaukee Area Technical College, WDJT reported.

"Obviously it required some ingenuity for an individual to do something of this nature in, literally in an urban area, an urban setting, and it go undetected for any period," Milwaukee County Sheriff Eaernell Lucas told WDJT.

The entrance to the encampment was concealed and the college had not given anyone permission to live on the land, the Sheriff’s Office said.

“Our investigation has not determined the exact length the individual may have been inhabiting in this encampment, but it's conceivable it may have been a considerable period,” Lucas said at a news conference.

Graff had fired a gun three times in frustration after his dogs ran away, bringing attention by law enforcement to the area, investigators said.

Graff had four guns, three knives, a bow and arrow, supplies, a grill, propane tanks, a generator, and numerous hand and power tools, Lucas said.

Deputies are still investigating.

Graff is in custody and could face weapons and trespassing charges, but none have yet to be filed against him.