Considering the cyclist tried to walk away.......
a) That was filmed in the Bronx......I know the area, (Live in the Bronx)
b) People here carry and use things you do not see right away like razors, small knives and watches around their hand.
c) I would've done the same until the attacker was down. You don't take chances around here.
The guy surely did not look like a bike messenger.