OP is referring to them as brown shirts because they're being used for intimidation, amassing in blue cities like Minneapolis instead of red states that actually need and want immigration enforcement.
The reason there are so many federal agents massing in "blue cities" is because the criminal illegal immigrants (a distinct sub group of illegal immigrants, who are themselves a distinct subgroup of all immigrants) in the "blue cities" are released onto the street by "blue city" police because "blue city" politicians tell them to, and refusing to hand them over to ICE at the prisons and jails they are in (a controlled hand-off). So, to collect a rapist, spouse abuser, etc ICE has to roll into a neighborhood and pick them up at home. Instead of requiring two ICE officers for a controlled hand-off, it can take a dozen or more to secure the location AND do crowd control when all the "blue city" residents show up and protest removing the criminal illegal immigrant.
Conversely, "red states" participate in controlled hand-offs so there is no need for a dozen or so agents to roll into a neighborhood to pick up a convicted rapist, etc.
Oh, and when ICE agents enter a room to capture a wanted criminal illegal alien, their SOP is to determine the immigration/citizenship status of everyone in the room, removing anyone illegally in the country from the room as well.
As for the "shooting of U.S. citizens", the two deaths we know of prove that it is very dangerous to lay hands on a federal agent while arresting someone (esp, but not only, when you are carrying a loaded gun) OR to not put yourself in a situation where you hit a federal officer with your car. Those are the reasons two U.S. citizens were shot.
H, and for completeness, the 5 year-old boy wasn't used as bait to capture his dad, he was with his dad when ICE went to capture him, his dad ran away, abandoning his son in front of ICE agents, and because democrats have whipped the immigrant community into such a frenzy the boys own mother refused to open the door to let him in his own home. ICE asked the father what to do, he (the father) REQUESTED to keep the 5 year-old with him in detention... To the father that was preferable to Child Protective Services, and the boys own mother refused to reclaim her 5 year-old from the agents.