Some context would be useful here and there's little available just yet, but here's what appears to have happened:
Incident takes place in Clark Park, Philly. Proud Boys for the last couple weeks circulate a bunch of digital flyers for a PB rally to take place here; they later claim it was a hoax designed to entice Antifa out and that they (PB) never planned to attend.
Community members and counterprotesters/Antifa show up but no PBs. Conservative media pundit covering the rally gets heckled by locals/CPs/Antifa mob, during which anonymous dude who some report is PB-type, others say is a counterprotester mistaken for PB-type, approaches scene from the side with a bat or rod and bangs the pavement with it, and mob-focus turns to him.
Conservative pundit and anonymous dude get chased off the scene, and most report the vehicle getting bashed by Antifa (or Antifa wannabe) shitheads is anonymous dude in case of (deeply ironic, if true) mistaken identity or dumbass agitator who looked for some trouble and found it.
Point being, at least so far it doesn't appear to be Antifa thugs targeting blameless good citizens; doesn't justify the behavior at all, just not gonna get too stirred up over it if as reported. Something about stupid games...a prize...something.
Not ideal sources based on their framing, but they're best available at present...
https://www.inquirer.com/news/proud-...-20200919.html
https://www.rt.com/usa/501177-antifa...rs-attack-dog/