In this situation, it can't be just one person. Several people need to call 911 with plate numbers and general descriptions.
"A bunch of people in masks waiting outside the court house. I think they have guns!"
If ICE has done their due diligence, they would have notified law enforcement that they are there in plain clothes. But methinks that these cosplayers wouldn't think to do that.
I worked with someone who was working on his second PhD in computer science and the guy did not know how to print.
Literally couldn't figure out how to click the print button.
In computer science.
PhD.
Computers.