then just the indented message goes out. when we would find these indented messages in their paperwork, and they would hide it amongst their legal documents as well, then they would open up envelopes and do the ghostwriting on the inside of the envelope, reseal the envelope, place some insignificant communication inside the letter and send it out. >> officers in the mailroom review an average of 300 to 500 letters every day, looking for any clues of impending gang activity. >> one gang member down in a prison in southern california wrote to three different mexican mafia members, identifying people in that institution he wanted to kill. [ speaking in spanish ] which means "i want to take jimmy to the barber as soon as possible." we caught two of those letters, but we didn't catch the third one.