Possible. When Berkeley invited Milo to speak, antifa showed up first and broke quite a few windows, same way antiglobalists reliably start riots anywhere G-7 meets. [0]

After that alt-right brought in their own thugs as well, which might be the ones you're referrring to.

In the antifa vs. alt-right contest both sides get a dishonourable second place.

[0] https://en.wikipedia.org/wiki/2017_Berkeley_protests