When the Gun Goes Bang, Bang, Bang is the tenth episode of the first season. It first aired on September 13, 2010 and drew 6.56 million viewers. It was written by Janet Tamaro and directed by Michael M. Robin.
The day starts with a party to welcome Jane's brother home from prison and ends in chaos when killers storm police HQ.
The entire homicide division is present at a warehouse, when an undercover homicide cop is shot dead. Upon arrival back at headquarters, Rizzoli interviews a witness to the murder, but things go awry when the drug dealers responsible storm headquarters at gunpoint and shoot dead the on-duty cop working the desk. Whilst everyone at the crime scene remains none the wiser, a desperate Rizzoli and Isles try to save Frankie's life, when it hangs in the balance on Maura's table after he is also shot by the assassins. The day takes an even darker turn when Rizzoli is held at gunpoint by the man responsible, the last person anyone ever suspected. In order to catch him, she makes the ultimate sacrifice.
- Angie Harmon as Detective Jane Rizzoli
- Sasha Alexander as Dr. Maura Isles
- Jordan Bridges as Officer Frankie Rizzoli, Jr.
- Lee Thompson Young as Detective Barry Frost
- Bruce McGill as Detective Vince Korsak
- Lorraine Bracco as Angela Rizzoli
- Brian Goodman as Lieutenant Sean Cavanaugh
- Erik Palladino as Detective Bobby Marino
- Chazz Palminteri as Frank Rizzoli, Sr.
- Jack Conley as Murray
- Sticky Fingaz as Kirk Jones
- Melonie Diaz as Witness
- Christopher Bello as Detective Danny Clark
- Tom Billett as Officer Jimmy Wolf