It has been verified by reputable media that twitter handle @antifa_us was a fake antifa poster organized by white nationalist group Evropa ([1],[2]). It's impressive there has been so much false action that is immediately discovered during this time.
In the small towns around the Seattle area there have been multiple false claims of antifa planned attacks, leading to lots of people pulling out their guns. Here's one where someone visiting from out of town took pics of kids walking around and made wild accusations that they were 'outsiders' who were threatening - yet he was the outsider who was making up threats. [3]