Prior to Season FourEdit
Some time prior to Season 4, Tretiak was a restaurant owner and a notorious arms dealer who dealt mainly with the Russian Mafia in Farmington, Los Angeles. LAPD Officer Carl Miller once gave a speeding ticket to Tretiak, which enraged him beyond borders.
The speeding ticket, and the fact that the police had captured Tretiak's associate Kozodav, convinced Tretiak that the time is right to get revenge against the police. He struck a deal with fellow cop-hating One-Niners gang leader Antwon Mitchell and then the two hatched a plan how to get their revenge on the police all while deflecting any blame.
With Jason Porter as an intermediary, Tretiak agreed to use Nigerian hitmen Ade Achebe and Idisa Okoye brought by Antwon Mitchell to kill Officers Wayne Haimes and Carl Miller. Porter also brought Tretiak language tapes, which he kept in his office.
After the two cops were kidnapped by the hitmen, they were murdered on Mitchell's and Tretiak's orders. The Strike Team managed to locate the dead officers in the two hitmen's residence. To their surprise, they also located there the dead body of Ade who had been killed by Tretiak's men to tie up loose ends. They also discover that Idisa and his family were kidnapped by Tretiak's men and were held hostage.
After stopping the hijackers and saving Idisa and his family, the team tracked down Tretiak and saw him beating a prostitute. They broke into his office and saw invoices for shipments at a warehouse. When they went there, Tretiak was with some of his associates, testing some C-4 explosives.
The Strike Team then planned to arrest him, but he wasn't at the warehouse at the time of the bust. Vic Mackey then sent Ronnie and Lem to pick him up at his restaurant together with his lieutenant and the prostitute whose name is revealed to be Irina.
They then took Tretiak to one of his warehouses, where Irina hit him in rage for all the beatings. After they pulled off Irina, they told her to translate for Tretiak as they questioned him about the murders of Officers Haimes and Miller.
The Strike Team then tie up Tretiak to a chair and rig him with some C-4. While they questioned his associate, a panicked Tretiak shook his chair and fell, triggering the C-4. The resulting explosion blew up Tretiak, killing him.
After Tretiak's death, The Strike Team fled with Irina and Osip. While in the van, Irina translated for Osip as he told them how Tretiak was connected to the murders of Haimes and Miller. At the Barn, Idisa also testified about Tretiak's role in the deaths of Miller and Haimes. Very soon after, Mitchell himself was arrested for his part in the murders of the officers and for the murder of CI Angie Stubbs and was sent to prison.
While trying to take down a Russian drug dealer, Vic asked Irina who works at the Russian's nightclub for information. After she made it clear that she is hesitating, Vic told her to give him some information or he will tell the dealer how she betrayed Tretiak.