Attorneys for the parents of 36-year-old Jeremy Dowell filed a federal lawsuit Monday, alleging that his killing by Lynnwood police Officer Zachary Yates was unjustified even though investigators concluded Yates had acted reasonably during the Jan. 30, 2017, incident.

When a team of Snohomish County investigators found that a Lynnwood police officer had acted reasonably when he shot and killed a knife-wielding man on Highway 99 last year, it looked like an open-and-shut case.

Detectives found that 36-year-old Jeremy Dowell came at Officer Zachary Yates with the knife, minutes after Dowell had frightened people at a carpet store, made a reference to the Islamic State and darted into busy traffic.

The Snohomish County Multiple Agency Response Team, commonly known as SMART, investigated the Jan. 30, 2017, shooting and concluded that it fell within legal standards.

But since then, 12 witnesses contacted by an attorney for Dowell’s parents have signed sworn declarations challenging the official version in stark and sharply critical language. Although no one disputed that Dowell was carrying a knife, six people who said they saw the initial confrontation said Dowell never directly threatened Yates.

Ten of the witnesses said Yates continued to fire shots at a helpless, stumbling or severely injured Dowell. Five said some rounds were fired while Dowell was on the ground.

Some of the witnesses also complained that they weren’t contacted by detectives after giving statements at the scene.

The witnesses’ declarations, coming from people from various walks of life, are striking in their number and consistency. Half the witnesses described the shooting as a murder.

“What I saw was so deeply disturbing that the memories haunt me to this day,” Nadeem Pasha said in a declaration. He called the shooting “completely unwarranted.”

The witness statements are contained in a federal civil-rights lawsuit filed Monday by attorneys Ed Budge and Erik Heipt on behalf of Dowell’s mother, Suzette Dowell, and stepfather, Robert Dowell, accusing Yates of “outrageous and reprehensible use of deadly force.”

The suit, which names Yates individually and not the city of Lynnwood, alleges he “quickly jumped out of his patrol vehicle, pursued Mr. Dowell on foot, and almost immediately began shooting him.”

It further alleges that the SMART team — made up of investigators from various county law-enforcement agencies and the Washington State Patrol — conducted a biased investigation, deliberately steering the outcome to clear Yates of any wrongdoing.

The purpose behind SMART is to ensure public trust, by carrying out professional investigations and keeping departments from conducting investigations of their own officer-involved shootings.