TOWN OF BARTELME, WI (WTAQ) - Authorities in Shawano County are investigating an unusual ATV crash that critically injured a 5-year-old boy. 

The call goes out about 4:20 p.m. Monday to a residence on private property off MohHeConNuck Road in the Town of Bartelme on the Stockbridge-Munsee Reservation.

"A 5-year-old child was operating an ATV with a 4-year-old passenger," says Stockbridge-Munsee police chief Jim Hoffman. "The ATV collided with a tree, injuring both children."

Neither child was wearing a helmet.

The boy was airlifted to St. Joseph's Hospital in Marshfield. The 4-year-old girl was treated at the scene and released.

Hoffman says the crash remains under investigation. The kids' mother was apparently visiting a friend who lived at the property at the time.

Officers from the Stockbridge-Munsee Conservation Department, Shawano County Sheriff's Department, Stockbridge-Munsee EMS and Fire Departments also responded to the scene.