The cop knows what he has on his utility belt.
What I don't understand, is why cops are so reluctant to create some space between themselves and the suspect and analyze what is going on. Cops never seem to retreat from anything, they just pull their guns and shoot. Take a few steps back, create some space, and give yourself time to actually make a humane decision.
To me, it looks like the guy took the cop's extra clip. But let's say it's an unopened knife. The guy appeared to be in absolutely no hurry to open the knife, he seemed like he was high and moving in slow motion. He was brushing hair away from his face when the cop first shot him.
So what is stopping the police officer from holding the man at gunpoint, while he backs up about 20 feet while telling the guy to drop it? Instead, he just pulls his gun and shoots him 7 times?
I defend cops when they do things that make sense. When I see that video, I do not see a guy who needed to be shot. If more evidence surfaces that changes my interpretation of what happened, I'm happy to change my conclusion.