But three other jurors said it's unknown whether Williams posed a threat, and only four of the eight said definitely that the woodcarver did not pose a threat to officer Ian Birk before the deadly shooting.
Birk's attorney said this question is crucial to the case.
"We believe the important questions is whether or not Ian Birk believed that he was at risk," said Ted Buck. "The is the one who has the training to ascertain when these kinds of risk arise."
The jury's findings came after nearly two weeks of testimony from Birk, witnesses and members of Williams' family, as the presiding judge read them in a hushed King County courtroom.
The jury also was divided about whether Williams had enough time to drop his knife before Birk shot him dead Aug. 30 on a Seattle sidewalk.
One juror said Williams did have enough time, but four others said he did not and the remaining four said it was not clear whether he had enough time.
All eight jurors agreed unanimously that Williams, a First Nations tribal member, had a knife in his hand when Birk fired his weapon.
But four of the jurors said the blade was not open at the time of the shooting, and the four others said it was unknown. None of the eight said definitely that the blade was open.
Jurors also were divided on the question of whether Birk himself believed that Williams posed a threat of serious physical harm. Half said, "Yes," the other half said it was unknown.
The woodcarver's family members reacted to the jury's findings with tears and a call for justice.
"Four-point-something seconds to make a decision. What are you, God? Are you?" said Williams' brother, Rick Williams. "Drag my family through the mud. All we wanted to do is keep heritage alive."
Birk left the courtroom without comment and with a police escort.
"Of course, I want to see him prosecuted," said Rick Williams. "Going to play God with my brother and my family. Damn, my granddaughter said to me, 'To protect and serve...Grandpa, as I see it, it's protect and shoot people like me."'
"This is as about as clear an indictment of the officer as you can possibly get from an inquest jury," said Tim Ford, the attorney representing the Williams' family. "On all the contested questions, there is a significant majority that says this was not justified."
Prosecutors will use the inquest jury's findings to help decide whether a criminal charge against Birk is warranted. The review is expected to be completed by mid-February.
During the inquest, Birk claimed Williams was swinging a carving knife in his direction, leaving him with no choice but to open fire.
Dash cam video from Birk's patrol car captures the sights and sounds of the incident.
But other witnesses questioned that version of events, saying they didn't see Williams pull a knife on Birk or lunge at him.
Evidence admitted during the inquest also revealed that Williams' knife was found in the closed position after the shooting.
The drama unfolded on a sunny day at the end of August 2010. Birk was patrolling in his squad car when he spotted Williams ambling across the street in a croswalk.
A dash cam video in the patrol car showed what happened next.
Officer Ian Burke can be seen walking after Williams and shouting, "Hey, hey, hey! Put the knife down! Put the knife down!"
The officer walks off-screen, shouts again, and then five shots ring out in rapid succession, killing Williams.
From the moment Birk gives his first command, Williams has seven seconds to react until the first shot is fired.
Here are the jurors' answers to a series of questions they were asked to answer:
1. On August 20, 2010, did Seattle Police Officer Ian Birk observe John T. Williams crossing the street? Yes 8
2. Was John T. Williams holding an open knife at the time he was first observed by Officer Birk? Yes 8
3. Did Officer Birk get out of his patrol car to contact John T. Williams? Yes 8
4. Did Officer Birk gesture to John T. Williams to come back to Officer Birk's location? Yes 7 Unknown 1
5. Did John T. Williams have a knife in his hand when Officer Birk contacted him? Yes 8
6. Did Officer Birk order John T. Williams to put the knife down? Yes 8
If your answer to question 6 was yes, please answer the following four questions:
6a: Did Officer Birk order John T. Williams to put the knife down more than once? Yes 8
6b: Did John T. Williams have sufficient time to put the knife down after Officer Birk's order? Yes 1, No 4, Unknown 3
6c: Did John T. Williams try to put the knife down after Officer Birk's order? Unknown 8
6d: Did John T. Williams put the knife down before Officer Birk began to fire his weapon? No 8
7. Was the front of John T. Williams' upper body partially turned towards Officer Birk when Officer Birk began to fire his weapon? Yes 2, No 5, Unknown 1
7a: If no, was John T. Williams turning towards Officer Birk when Officer Birk fired his weapon? Yes 5
8. Did Officer Birk fire his weapon at John T. Williams on August 30, 2010? Yes 8
9. When Officer Birk fired his weapon, did John T. Williams have a knife in his hand? Yes 8
9a. If yes, was John T. Williams' knife blade open when Officer Birk fired his weapon? No 4, Unknown 4
10. Did Officer Birk believe that John T. Williams posed an imminent threat of serious physical harm to Officer Birk at the time Officer Birk fired his weapon? Yes 4, Unknown 4
11. Based on the information available at the time Officer Birk fired his weapon, did John T. Williams then pose an imminent threat of serious physical harm to Officer Birk? Yes 1, No 4, Unknown 3
12. Did John T. Williams die in King County, Washington on Aug. 30, 2010? Yes 8
13. Did John T. Williams die from the gunshot wounds caused by Officer Birk? Yes 8