Tonight was the debut of a new MMA league called Professional Fighters League on NBC Sports.
Top ranked UFC welterweight contender Kamaru Usman and his manager Ali Abdelaziz were in the crowd and things got weird when a guy took a knee during the national anthem.
According to the person who uploaded the video, a guy was taking a knee during the anthem when he was confronted by Kamaru Usman and Ali:
Some dude that was kneeling at national anthem. Then Ali told him not to do that then and the other guy got mad then usman tried to hold them but someone swing a punch and then this is what happen.