Three people were taken to hospitals after the series of crashes along 128th Street SW, which becomes Airport Road. The tangle closed for hours the busy arterial that connects I-5 to Highway 99.
Two men were taken by ambulance to Harborview Medical Center in Seattle with critical injuries, officials said.
A woman also was taken to a local hospital. Her injuries were not believed to be life-threatening.
Tyler Byers, 27, was eastbound on 128th on his way to class at University of Washington Bothell when he realized he could be in trouble as a dark Lexus sped westbound toward oncoming traffic.
He could see the driver.
"He looked unconscious to me," Byers said. "He actually accelerated as he crested the hill."
Investigators believe the Lexus ran a red light, struck the first vehicle, side-swiped about 10 more and then rammed another vehicle head-on, said Kevin Prentiss, a bureau chief with the Snohomish County Sheriff's Office.
The driver who apparently had a medical emergency, a Mill Creek man, 60, was one of those critically injured.
The other victim, also in his 60s, was the driver of the car that was hit head on.
One of the crashes sent a teal Chevrolet Blazer into Byers' red 1994 Mustang Cobra.
The accident was reported at 3 p.m. near the intersection with E. Gibson Road west of I-5, said Leslie Hynes, a spokeswoman for Snohomish County Fire District 1. The crash scene spanned roughly 500 feet west of the intersection.
The two seriously injured men had to be cut out of their cars by firefighters, officials said. One of the cars caught fire.
The crash is being investigated by the sheriff's office Collision Investigation Unit. Detectives expected to remain on scene for several hours Monday night, Prentiss said.
"It sounds like maybe a diabetes issue," said detective Scot Fenter, who was investigating the sprawling crash scene.
The Lexus appeared to lose a wheel at the intersection of 128th and E. Gibson Road. It ended up crossing two eastbound lanes and climbing over a sidewalk before stopping in brush about 100 yards down the hill from the other cars.
The Lexus also crashed into another car that was pushed several yards down the hill. It ended up in a bramble-filled ditch with both airbags deployed.
Emergency crews from Lynnwood and Mukilteo also responded. Medics treated at least four people at the scene.
Eric Stevick: 425-339-3446; firstname.lastname@example.org
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