You have to speak into the microphone inside the room that you turn off the camera. Once you do that the cop will leave and then he will tell you where to get the keys for the handcuffs ("in case you want to tighten them" he says). Grab the jacket off of the chair in this same room and then go get the keys off of the officers desk. His desk is next to Blake's, if you are facing Blake's desk so you are looking at him directly it is the one to the left. Now go help out Ethan and he will walk out on his own.