Per
NPR (a solidly left-leaning source) they were US Marshals and they used unmarked vehicles to avoid the violent protesters who were allegedly targeting police. They didn't arrest anyone, but transported them to a safe location for questioning and immediately released them. Certainly not a good look but
obviously this is nothing like SS troopers kidnapping people for death camps, torture, imprisonment, etc.
I am a vocal critic of Trump, but I don't understand the impulse to invoke absurd comparisons between the US and Nazi Germany. Trump gives us plenty of legitimate stuff to criticize on a regular basis, why discredit yourself like this?