Know that you're compromised. Don't say or do anything incriminating. If possible, leave.

Switch off the phone, then leave.

Never turn off your phone if you think you're in trouble; this creates an anomaly in the data, akin to acoustic shadow.

I would write a twit about government doing the authoritarian tilt so other people can do something about it. Raising awareness is important.

Interesting question for sure. Given the implied budgets for domestic surveillance, are there any metropolitan areas which do not have fake towers?

What is the point of stringrays anyway? It's a thing that exists, so I believe it does something, but I can't figure out what exactly.

They can go through the area, catch a whole bag of IMSIs and then.... what? What capability does it enable? Knowing when a certain person of interest shows up in a certain locality? Can't they get it from the phone company without a warrant anyways, just by asking nicely? If it's not targeted, what the data is even used for theoretically?

Stingrays are use to intercept calls in real time. They are used by police and foreign intelligence agencies. It allows them to listen in on political calls. Washington DC is a haven for fake cell phone towers.

I found out the LEO in the area I was in had at least one. I saw a police car parked in the area I was in. Very out of place and would only be there if there was a house call. Decided to test the waters, went out side, paced back and forth, and kept talk. His face and body language changed dramatically which let me know he was using a Stringray and I was the current target without a warrant.

Real time collection and less legal friction?

Completely unrelated thought, but it sure is a crying shame that goatse.cx died. :(