Revealing mistake: In the scene where Cooper takes the homeless man's photo on his iPhone, if you look to the bottom left of his iPhone's screen where it shows pictures that you have already taken, you can see that the homeless man's photo has already been taken, indicating that perhaps this scene was shot a few times, and the photos taken during those scenes were never deleted.
Underwater - S4-E2
Continuity mistake: Sammy Bryant has been a three stripe Sergeant throughput the series. In this episode's roll call he's wearing two stripes.
Continuity mistake: Near the end of the episode when a gunman enters the precinct house and starts shooting, Sammy dives for cover and begins looking for his gun in his duffle bag - twice.
