This is extremely disturbing, and further evidence that the U.S. is a police state. I've never felt more ashamed of my country.
The video camera turns on while they were (likely) already told they will be arrested. They were perhaps ordered to move and did not move. The National Guard and state troopers in that particular area (< 15 miles from me) started ordering people to disperse or face arrest. I don't believe that press are exempt from this order especially when a state of emergency is declared.
Downvoters: please add comment why, or else this isn't discourse
What chaos? The scene shown in the video looks really calm, with one protester, several reporters, and a very large number of police standing around apparently doing nothing more than looking intimidating at that moment.