SALEM, Ore. -- An alert driver exiting Interstate 5 in Salem early Wednesday acted on his instincts when he saw a couple struggling against each other on the ground. He stopped to find out what was going on and so doing stopped a rape in progress, according to police.

Salem Police said a 43-year-old transient raped a woman twice in roadside bushes near the I-5 exit ramp at Mission St.

Darrell Root allegedly dragged a 43-year-old woman into the bushes and raped her just after 2 in the morning Wednesday. At some point she broke free and ran away, only to have Root catch up with her, strangle her until she passed out and then rape her again, Salem police said.

Pete Saleen saw the woman just as she broke free from Root. Saleen was exiting the interstate and couldn’t decide whether the two were acquaintances having an argument or if he was witnessing an assault.

Saleen didn’t take a chance. He pulled over to call police at a Denny’s restaurant, where he happened upon two officers.

Police quickly headed to the area and found Root in the act of raping the unconscious woman, with a belt around her neck.

“This attack was very brutal. It was up-front and it was very violent. We believe very firmly that (Saleen) reporting this to us … quite possibly saved her life,” Lt. Dave Okada said.

A public records search indicates Root is a registered sex offender in Alaska.

He was charged Wednesday with attempted murder, first-degree rape, strangulation, coercion, and attempted assault.

The victim, also a transient, was being treated at Salem Hospital, police said.