I watched the video. It's disturbing.
A police dash cam at a red light. A man in the crosswalk walks past the front of the car. He is cradling a board in his left arm, he has a knife in his right hand and he is carving on the board as he walks, head bent over his work. He reaches the sidewalk and exits frame to the right.
The officer gets out of the car, and is seen walking across the camera view, exiting frame right. He begins to shout "Hey! Hey! Hey!" as he gets on the sidewalk. Immediately after this, you hear him say "Put the knife down. Put the knife . . . DOWN! Put the knife down." immediately followed by 5 or 6 quick shots. He then radios something like "blah blah shots fired, suspect down, he wouldn't drop his knife"
Later he is heard yelling to someone "Because he wouldn't drop his knife!"
He repeats to other officers at least two more times that he fired because the guy wouldn't put down the knife. Not "he came at me with the knife" or anything like that.
Now, I am of the mind that deadly force laws do not exist to provide a set of circumstances where you can shoot somebody if you want to. I feel that deadly force laws presume that there will be cases where an innocent person needs to use deadly force, and those innocent people, who were thrust into a terrifying and dangerous situation, deserve protection from the law for what they were forced to do.
All too often I see this mindset where people say "well, if they do X, then you can shoot them." and I think the point of the whole thing is missed. I think normal people do not want to shoot anybody, and will avoid doing so at almost all costs. But when they do, deadly force laws are in place to weed out the good and bad shoots.
I think this is a bad shoot. I think the officer thought "he's not dropping his knife, I can shoot him." and so he did.
IANAPO and IANAL, but consider this: his own department ruled it was an unjustified shoot and have fired him. The DA has stated that the only reason he is not being charged is because he was a peace officer at the time, and WA has some interesting laws regarding peace officers and deadly force. Specifically, the state has to prove malice beyond a reasonable doubt to convict a police officer in any shooting.