A 9-year-old boy operating a recreational utility vehicle crashed it on western Minnesota farmland and was killed, authorities said.

The rollover late Thursday afternoon in a Millerville Township hay field behind a home also injured the boy’s 10-year-old sister, who was his passenger, according to the Douglas County Sheriff’s Office.

The boy was identified as Jon T. Dingwall Jr. of Brandon, Minn.

Neither Jon nor his sister, Taylor Dingwall, was wearing a helmet while on the Polaris Ranger XP side-by-side utility vehicle, the Sheriff’s Office said. The siblings’ parents are Jon and Kami Dingwall.

Capt. Jon Paurus, education coordinator for the state Department of Natural Resources, said Monday it is illegal for a boy that young to be operating such a vehicle and also too young to have a passenger along.

"The key with all these youth crashes is lack of parental supervision and guidance," Paurus said.

Jon Jr. was pinned under the machine when emergency responders arrived, the Sheriff’s Office said. His sister had gotten out from under the vehicle.

A sheriff’s deputy freed the boy and began resuscitation efforts along with other first responders. An air ambulance took the boy to Hennepin County Medical Center, where he was pronounced dead early that evening.

The medical examiner’s office in Hennepin County said Sunday that the weight of the machine prevented the boy from breathing.

The Sheriff’s Office continues to investigate the circumstances surrounding the crash.