I didn't watch the event and wasn't there, but from what I've gathered this morning:

That's Sean Strickland, a 💰UFC💰 fighter and he's been pretty vocally anti-Israel and still thinks the Epstein files are a big deal. Unsure on his feelings towards Trump specifically anymore (previous MAGA I believe) but he was in some way discouraged from attending this event because of his outspokenness about Israel and Epstein.

He showed up anyway (not wearing the shirt in the image, that's fake afaik) and got some sort of fighting pit started with fans where he was lightly sparring with people and it caused a crowd to start forming. That's when security/police stepped in to escort him out.