They did the same thing during the Occupy Wall Street movement protests. There is a video of federal agents pulling protesters off the street and into an unmarked car, during that time. The federal response to these protests is far lighter than their response to that protest movement was, they've arrested a lot fewer people and have been far less physical with the protesters. They're using many of the same tactics though:
https://www.theguardian.com/commentisfree/2012/dec/29/fbi-co...