Of course, we can't be certain, but it seems pretty likely that the video feeds went dark at the behest of those in power who wouldn't want viewers to see a militarized police force in action. I had a related experience during the 1999 WTO protests in Seattle.
I had been arrested (inadvertently, honest!) on the second day of the actions, and many hundreds of us spent 15 hours or so on buses while the police figured out how to get us off and fully into their custody. To make a very long story very short, they waited until after the 11 o'clock news teams had left (the parallel to Lili Loofbourow's excellent story here) to take action.
That action was extremely ugly and violent. The details are common as dirt. They involve one of the unwritten parts of the policeperson's job description: render a preliminary judgment and dole out punishment on the spot. There were injuries inflicted, of course. And the police made certain their riot would not be televised.