A nursing supervisor at Harborview Medical Center in Seattle says the man died Monday night shortly after his arrival. He has not been identified.
The drama unfolded just before 7 p.m. Monday when the man stopped his truck on the Ship Canal Bridge, set it on fire and spray-painted a large green circle on the freeway.
A driver who called 911 to report the incident told dispatchers the suspect "looks insane."
"He literally looks crazy. He's outside of his car -- and the car's on fire -- holding something, putting his arms up in the air. It looks terrifying," the man said.
Two Washington State troopers and a state Department of Transportation incident response employee arrived on scene quickly. One of the troopers and the DOT employee began to extinguish the flames while the second trooper contacted the suspect.
The suspect displayed a knife and advanced on the trooper. The trooper used his Taser but it did not subdue the suspect, said Drew Fowler of the Seattle police.
The man continued to advance on the trooper with a knife. Both troopers then fired at the suspect, stopping him.
The troopers have been identified as Andrew Boyer and Christopher Kyle, both 29-years old. Boyer is a 7-year veteran of the state patrol currently assigned to the Bellevue District Office. Kyle has been a trooper for two years and also works out of the Bellevue District Office. Neither trooper had used deadly force prior to Monday's shooting, according to WSP.
Seattle Fire medics took the suspect to Harborview for treatment of life-threatening injuries. He died shortly after arriving.
Detectives shut down all southbound lanes of I-5 just north of the Ship Canal Bridge for about five hours for an investigation.
The incident backed up traffic for miles. Troopers turned some cars around and diverted others. Some bus passengers got out and walked.