The crash happened at 10:16 p.m., just north of I-405, according to a Washington State Patrol memo. The ramp to southbound I-405 was closed at the time due to an earlier collision.
A Kenmore man, 32, driving a 2001 Ford Focus failed to slow down for the closure.
The Ford struck a Suzuki, which was pushed into a Mazda. The Ford then struck two additional vehicles.
The Kenmore man was taken to Harborview Medical Center in Seattle. He was listed in serious condition in the intensive care unit.
He is under investigation for vehicular assault, according to the memo.
At least three others were taken to a local hospital with less serious injuries from the collision.
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