And if it wasn't tear gas, it was some sort of irritant
Look at about 4:16 of the video; there are various booms and then clouds of white gas. I couldn't see who launched it, but it came from the direction where the police were located.
https://twitter.com/hunterw/status/1267851877389078530?ref_src=twsrc%5Egoogle%7Ctwcamp%5Eserp%7Ctwgr%5Etweet