human interactions and the witness

Saturday afternoon I was in the corner store on 4th ave/9th street and two guys were in front of me in line: the African American one appeared homeless and/or mentally ill and the White one was wearing a trench coat. "You got a problem with me?" the Black guy kept asking the White one. "Why you looking at me funny?" etc. The trench coat was trying to ignore him, and he left the store. However, the Black guy followed him outside, where my roomate was waiting for me, and it escalated very quickly. A little way down the block the white guy was yelling, "You're messing with the wrong guy! I'll fucking kill you!" And then the crazy guy threw his breadroll at him. The trench coat rushed back and put him in a headlock, with a gun to the guy's head! Everything started to go in slow motion and it was very quiet. It seemed like nobody else around noticed what was happening. I started backing into the street and almost got hit by a car. I don't know what happened next because I walked away.