The single-vehicle collision killed the truck's driver, Mitchell S. Casey, 28.
Police believe he missed a turn and struck the barrier. He was rushed to a local hospital, where he later died.
The crash happened about 3 p.m. in the 4300 block of Broadway, where a bridge takes the road over an I-5 onramp.
The case has been under investigation by Everett collision detectives and the Snohomish County Medical Examiner's Office.
Casey died from blunt-force injuries, the medical examiner's office said this week. His death was ruled an accident.
Everett police have ruled out speed as a factor in the crash, said officer Aaron Snell, department spokesman. They don't believe Casey was wearing a seatbelt at the time.
Detectives are waiting to review additional laboratory test results.
"We don't want to make a judgment off anything until we have all the results," Snell said. "We want to make sure, in the end, our conclusions are based on fact and not just what we see at the scene."
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