Here's the link. The section of video you're describing follows a discussion on the stolen laptops (starts around 20:30 and the SF guys are a few minutes after that.) He slows it down and discusses frame by frame. The patriots tried to stop these guys from entering. A woman is screaming "Antifa!" You see a guy up on the balcony, also wearing a backpack, yelling, "Let him go! Let him go!" while the first of the three guys on the stairs is shrugging off the people trying to stop them. Then the third guy wearing the stocking cap turns back to the camera and says, "We're not here to be Antifa!"
So it looks like at least 4 of these guys, probably more, came in with the crowd.
ThanQ, ponygirl!