When the police are about to enter the observatory where Gideon was hiding they had their cars parked in front of the entrance with flashing red and blue lights turned on.
As the police leave the observatory and Gideon is watching them from a distance you can't see any cars and there is also no flashing red and blue lights from the cars.
When the team first enters Carruthers' office and Crawford is explaining who he is, the actor portraying Carruthers (presently deceased) can be seen blinking from over his shoulder.