To partially answer my own question, here is a video of men in camouflage taking someone into an unmarked vehicle. There is no riot or other sort of violence on the part of the protestors in sight. I found this video via a Washington Post article about Constitutional rights around arrest.

https://mobile.twitter.com/greg_doucette/status/128345258594...

https://www.washingtonpost.com/outlook/portland-fourth-amend...