Gibbs realizes the Captain is suffering from post-traumatic stress disorder, but knows his experience overseas may also provide a key link to the crime.

More inconsistencies surface when Ducky's autopsy reveals that Torres was not beaten by a gang of men, but by only a pair, which contradicts Westcott's account.

Gibbs then has Westcott tell him about the story of how his squad was ambushed by insurgents in Iraq shortly before their tour of duty ended.

Westcott can't forgive himself for succumbing to cowardice and it is revealed that he suffers from post-traumatic stress disorder, as he is constantly reliving the ambush in his mind.

Unfortunately, McGee gets hold of Tony's embarrassing old high school portrait and Ziva gives him a relentless amount of grief.

[3] On September 13, 2012, TV Guide announced that Brad Beyer would guest star as Marine Captain Joe Westcott, who "shows signs of post-traumatic stress disorder".

[4] Together with Beyer, Glen Powell was cast to portray Westcott's brother Luke and Mark Rolston as their father George.

"Shell Shock (Part I)" was seen by 17.05 million live viewers following its broadcast on November 13, 2012, with a 3.1/9 share among adults aged 18 to 49.