I think the following guy is antifa, but I am not sure, since the term is vague and there is no official registration site. Presumably, it is a catch-all category for those from the Left who want direct action, typically involving violent protests, like this:
https://nypost.com/2018/08/09/man-arrested-for-tweet-offering-to-pay-anyone-who-kills-an-ice-agent/
“A Massachusetts man who offered on social media to pay $500 to anyone who would kill a federal immigration officer was arrested Thursday, prosecutors said. Law enforcement officials said they hope the arrest of Brandon Ziobrowski, 33, sends the message that they will not tolerate what they described as a rise in threats against immigration officers and others amid increasingly heated political debates. “The agents and officers out there enforcing federal laws are doing their job, plain and simple,” U.S. Attorney Andrew Lelling told reporters. “Those who disagree with their mission are of course free to say so. But there is a difference between public debate and intentionally putting others in fear of their lives,” he said. Ziobrowski, of Cambridge, is charged with using interstate and foreign commerce to transmit a threat to injure another person. He was arrested in New York, where he was visiting a friend. He is expected to make an appearance there Thursday before being transported back to Massachusetts.”
