Personality and Appearance
Detective Hahn is a tall black man with major physical strength. He has a padlock-shaped facial hair and usually wears a suit. He is John's friend and pretends to be on his side even after John tried to beat him up but it turns out that he has been secretly coveting his wife, Alex.
Andy is first seen with John at the "Thou Shalt Not Commit Adultery" crime scene. He is later seen talking to John about the murders and then John gets a package from the Cortez and John thinks it is a bomb and evacuates the building. When the bomb squad is done looking John finds out it was a Oscar, maybe a murder weapon. Andy comes later to tell John that the Oscar was a murder weapon to one of the victims, Martin Gamboa. John tells Andy about the murders and how they might be connected to the Ten Commandments and James March. Andy doesn't believe John on this. Andy shows up with John at another crime scene, this time it was gossipers who got their tounges nailed to desks or the floor or some even ripped out the mouth. After the incident with Gabriel, Andy confirms that the blood on Gabriel was not his and that they are looking for a body. Andy is then worried for John when he is talking about a murder that happened 85 years ago where mutiple kids were killed and abducted. John finds Andy at another crime scene and Andy asks John what he is doing there because John was fired. John wants to see what happened but Andy escorts John out and says that they already have someone is custody. After John shots a gun by Scarlett, but aiming at Bartholomew, Andy comes with Alex to make sure everything is okay. Andy says that John is in bad shape and that he was talking about monsters. After that he drives Scarlett to her grandmother's house. John wants to know more about the murders but Andy won't tell him and they get in a fight and are forced to break it up. Andy tells a cop to watch over Alex and Scarlett and the cop obeys and Andy looks over Wren's body and then John shows up and thanks Andy for looking out for his family. John tells Andy he is the Ten Commandments Killer and that it all happened the first few times he went to the Cortez but Andy reminds him that he went to the Cortez a few weeks ago and that the murders happened a few months ago. John tells him that he first went in 2010. He reminds Andy it was the same day they went to the murder case with the dead children and farther. John then tells him about March and all the visits and how he killed Gamboa with the Oscar and then sent it to himself. He then says how he tried to kill himself but March freed him. He also tells him about his relationship with Sally and how she helped him with finding the two cheaters that were found nailed to the bed. He also tells Andy that March made him his succesor and how he killed all those people. John then tells Andy that he knows he wants Alex and he stabs Andy killing him.
- Last words to John: "You don't deserve Alex."