OSO, Wash. -

The Snohomish County sheriff's office says a 10-year-old boy was critically injured Sunday evening when he fell out of the bed of a moving pickup truck near Oso.

The boy was flown to Harborview Medical Center in Seattle with life-threatening head injuries.

Lt. Rob Palmer told The Daily Herald (http://bit.ly/1boUNGS ) the boy's father was arrested for driving under the influence.

Palmer says in almost all circumstances it is unlawful for passengers to ride in the bed of trucks.