EAST MACHIAS – A 4-year-old boy was killed Saturday morning when an ATV rolled over on him, the Maine Warden Service said.

The service said that Roy Denison, 37, was riding his two-seater ATV with his son and then was joined by an 8-year-old nephew.

While riding, the nephew accidentally stepped on the accelerator and the ATV rolled over an embankment,

The Warden Service said Denison, whose head was cut when the ATV tipped over, discovered that they had rolled over Wesley Keeton, 4, who is the younger brother of the nephew who was riding on the ATV.

Wesley Keeton was pronounced dead at the scene.

The Warden Service said the state Medical Examiner’s Office and Washington County District Attorney’s Office have been notified and the incident remains under investigation.