I believe the drones are probably more like the quad copters you can purchase from hobby stores. Not the Reaper type drones a lot of us are thinking of.
The FBI have used them before to surveil the US population.
Guess the FBI can just fly them at night and not be seen/shot it?
Small drones like that are not used for surveillance, but for tactical assistance before and during an operation. You'd have to be pretty stupid to mess with a FBI tactical team getting ready to take someone down, that or the target, but then you're going down anyway.