Fight in the Tenderloin

So I was walking around in San Francisco's Tenderloin district when I noticed this guy in his car, arguing with one of the guys on the road-working crew. The guy in the car pulled into the alley just ahead of me and I could tell they were about to fight, so I pulled out my camera and ran around the corner to film it. This is what I saw. I can't be sure but it looks like the black guy pulled out a knife! Look at the video and tell me what you think...