https://6abc.com/post/immigration-agents-conducting-sweep-nycs-famed-canal-street-confronted-protesters/18055773/ This article says that it was started by people on their way home from work.

In response, a contingent of protesters, many of whom appeared to be on their way home from work, surrounded the masked officers, attempting to block their vehicle as they shouted "ICE out of New York" and called on other pedestrians to join them.

The thing to keep in mind is that while these random people did nothing (blocked a vehicle and called more people to join them) the incident became about them. ICE had to leave at the time. And, meanwhile, anyone undocumented could get out of there.

As more New Yorkers joined the fray, some of the federal agents retreated on foot, followed by jeering protesters and honking vehicles. Additional federal agents, armed with long guns and tactical gear, also arrived in a military tactical vehicle.

And now these agents have to harass a bunch of citizens instead of immigrants.

Protest is the first step towards doing stuff. Obviously I'd love to see more...radical...stuff, but protesting in front of ICE is better than nothing on such short notice.

Gotta be pretty far up your own ass to feel good about that stance.