Detective Shane Vendrell was Vic Mackey's best friend since before the formation of The Barn and the creation of the Strike Team. The second series prequel 'Co-Pilot' shows them working together as partners on a murder investigation. The strength of their friendship was evident in how they went to great lengths to save each other from trouble and how Vic kept Shane in the loop while leaving Lem and Ronnie out of some of his darker schemes. However, their relationship eventually became strained when Shane entered into a serious relationship with Mara, who was very demanding of his time.
The Strike Team robbed the Armenian Mob of millions of dollars, only to have it burnt by Lem, who feared that the money would tear them apart and cost them their freedom. Then, Vic and Shane's issues came to a head with Shane accusing Vic of taking other people's side against him when they are supposed to be best friends, and Vic calling Mara a bitch who has got Shane so twisted that he cannot think straight anymore. The two fell out, and the strike team was disbanded.
Shane and Vic reconciled after Shane got involved with the drug lord and gang leader Antwon Mitchell, who killed a young girl using Shane's gun. He offered to hand her body over to Shane in return for the body of Vic Mackey. Shane contacted Vic to meet him alone. After realizing Shane's innocence, the two worked together, along with Ronnie and Lem to save Shane's career and get Antwon behind bars. Once this was successfully done, the Strike Team was reunited and became close friends once again.
When Jon Kavanaugh launched an investigation into the Strike Team after arresting Lem for stealing drugs, Vic went to great lengths to try to save him, even trying to strike up a deal with Antwon to get Lem protection in prison. When the deal went sour, Lem was forced to go into hiding. Vic, Shane and Ronnie planned to escort Lem to a ranch in the mountains of Mexico where he would be safe from the law and any enemies who may want to kill him but the plan went awry when Aceveda told Vic that Lem was talking about the Armenian Money Train robbery. Vic confided in Shane that Lem may also talk about the murder of detective Terry Crowley.
Shane and Lem met, and when Lem refused to go into hiding in Mexico, Shane blew him up with a grenade. When Vic learned the truth, he confronted Shane, and he told Shane that if he ever saw him again, he would kill him. Shane drove off, calling Vic a hypocrite.
At the end of season six, Shane kidnapped Vic's family and locked them in a cargo container. Although Shane did this to protect them from Armenian mob boss Diro Kesakhian, Vic was enraged. At the beginning of season seven, after he learned the reasons behind it, Vic grudgingly allied himself with Shane in order to protect his family from both the Armenian Mafia and Mexican drug lord Cruz Pezuela. As time passed, however, Vic and Ronnie decided that the time had come for Shane to pay with his life for murdering Lem. They arranged for him to be assassinated by Pezuela's Mexican drug cartel. At the last minute, Vic has a change of heart and tries to call off the hit on Shane, much to the disagreement of Ronnie, but was unable to reach Shane on his cell phone. Although Shane's Armenian employers (including Ellis Rezian) were all murdered, Shane escaped and pocketed the payoff money. Vic tries to reason with Ronnie that he has known Shane for a long time and that he was never the person then that he has became now. He takes responsibility for corrupting Shane and believes there's still good in him, but advises that the two need to be wary of Shane now more than ever, as he will most likely start suspecting them and want payback for the attempt on his life.
Shane knows that Vic and Ronnie decided to retaliate by blackmailing a small time pimp into murdering Ronnie and preparing to murder Vic himself while giving himself an alibi. When the pimp revealed the truth to Dutch Wagenbach, Shane fled the Barn and went on the run with his wife and son. The series came to its climax as Vic resigned from the police force and set out to insulate himself from prosecution by hunting down and murdering Shane and Mara Vendrell.
However, Shane began blackmailing Vic by threatening to surrender and testify against him unless he was kept ahead of the manhunt. Ultimately, Shane was horrified to learn of Vic's immunity deal with ICE during a cell phone conversation with him. As a result of Vic's taunts, Shane murdered his pregnant wife, Mara, and his son Jackson by poison and then shot himself in the head.
In the series finale, Vic placed a picture of himself and Lem on his new desk at ICE headquarters. Though originally, the picture was of all four members of the Strike Team, Vic seemed to have cropped Shane and Ronnie out of the frame, unable to reconcile himself with Shane's betrayal of Lem and subsequent suicide.