Let me help you.
1. The guy wearing white with the backpack is the man who was shot.
2. The guy doing the shooting is wearing tan pants and a dark top.
3. There is a guy on a skateboard passing behind guy #1,
4. You can see guy # 2 walking up (saying "right here?) then you see his right arm come up and shoot twice, then he turns around and calmly walks away.
Even if we accept his allegation man #1 had a knife, which is not evident in any video showing those reacting to aid the shot man, he was not close enough to use it. Nor is there anything showing man #1 was moving towards his shooter.
You seem to have that totally backwards. The guy in the dark top turns around and walks away, and then collapses face first. Watch the whole video:
Portland Shooting (8/29/2020) - Timeline Reconstruction [VERSION 1] - YouTube
Here's what I see, after watching this frame by frame a dozen+ times (using the time stamps on the "enhanced video")
https://twitter.com/i/status/1299937196292669440
1. At 0:01, a man in a black top and light shorts ("the Victim") is standing in front of the garage entrance on the right side of the street, facing into the street. There's a car on the side of the street right next to him, a little to his right. A man in a white shirt and dark pants, with what appears to be a dark backpack ("the Shooter") is in the middle of the street crossing from left to right (toward the side the Victim is on). Another person ("the Other Guy") appears to be crossing near the Shooter, just a little further away from the camera. Both are heading pretty much directly across the street to cross almost right behind the car and close to the Victim (perhaps a little "this side" of the camera from him).
2. At 0:05, just after the white SUV passes by, the Shooter seems to have veered a little bit to his right while crossing so as to get further away from the Victim. The Other Guy has made it pretty much all the way across (you can't see him well, as he's directly behind the Shooter). The Victim has turned generally toward the camera and is now walking purposefully down the street in the direction of the Other Guy (and the Shooter). He appears to be holding a fairly large object in his right hand, hanging straight down by his side.
3. At 0:06, the Shooter quickly turns his body 90 degrees in the direction of the Victim and appears to raise his arms in front of him (watch his right elbow and his shoulders). A split second after this motion, the Victim raises his right arm (and the large object) and you can see a cloud start to move toward the shooter. Before the cloud is even halfway to the Shooter, two shots are fired. The Shooter then backs away and runs off. The Victim turns up the street, walks about 15 feet and then collapses face first on the ground. His friend, who kind of appeared suddenly after the shooting runs up to check on him.
I cannot figure out for sure what happened to the Other Guy. I think he was probably just the Victim's friend who suddenly appears after the shooting right about where the "Other Guy" was last seen, and he was crossing the street more or less parallel to the Shooter while the Victim waited for him, and then they turned to head down the street toward the camera (and toward the shooter) with the Victim. My only hesitation there is that the Other Guy was a very dark outline, but the friend had a white shirt. This could be just because of the lighting, but it seems a bit odd.
But it's also possible that the Other Guy was the friend the Shooter mentioned, and that the Victim was approaching him quickly, which the Shooter interpreted as an attack. This makes it hard to account for the sudden appearance of the Victim's friend, and the absence of the Other Guy after the shooting, but it's not out of the question.