Before Season 1Edit
Carlos was in charge of the case of the murder at Nacho's gun shop. Assistant Chief Ben Gilroy decided to put Vic Mackey and Shane Vendrell in it as well. After being introduced they walked out of the shop and Carlos started comforting gang member Train Guttierez, whose pregnant girlfriend was one of the victims. Mackey argued with his method of befriending the gang members, but Carlos told him that building trust with them worked. After interrogating one of the gang members, Mackey told Carlos to look for the missing janitor while he went to talk with Wet Willie. After that, a gang member called Carlos and told him where he could find Jaime.
After Mackey talked with Wet Willie, Carlos told him about Jaime and they went to talk with him. After some convincing, Jaime told them that the killer didn't belong to any gang and that he was white. Carlos and Vic went to the Barn and told Gilroy what they had found. They then met with Latino activist Raoul Jimenez who demanded action. Although Vic disagreed, Carlos vouched for the LAPD to release the sketch they had drawn with Jaime's description.
Carlos then received information that the killer had started another shooting in a grocery store. He looked for Vic and they went there. After being briefed by Officer Danny Sofer, they went to talk with the owner of the store, Leon, whose son was among the victims. He told them that he managed to hit the killer with a baseball bat but didn't know which way he left. After they found the killer's car parked outside, they managed to identify him as George Michael Klassen. They then went to his house only to find his in-laws shot to death, but no signs of George or his wife and son. As Vic questioned George's sister, Carlos ordered the officers to canvass the area.
Vic and Carlos returned to the Barn to brief Gilroy on the case. Carlos told him that they had George's name and picture all over the city, and they were watching over his friends to see if he appeared. Vic left alone to try to do something else and returned with all the shop owners to corroborate their stories. As he met with Carlos and Gilroy upstairs, Carlos blasted him for pressing on a grieving father. After a brief verbal fight, Vic went to interrogate Leon while Carlos checked with the other store owners. As he got nothing, he went with Vic to continue pressing Leon. Eventually Leon confessed that he had captured George, and together with the other store owners, they gave him to The Toros for revenge. Vic and Carlos then ran out to see if they could find him before they kill him.
Carlos and Vic went back to Lucas and asked him where they had taken George and his family. He refused to talk and Vic threatened to beat him. Lucas told him that Carlos wouldn't let him be beat, but instead Carlos hit him in the guts and asked him again where George was. After he gave them their location, they went to find Train Guttierez had George tied, while he molested his wife. As they broke in the house, Train took Myra hostage and shot George in the head. After Vic injured him so he could release Myra, Carlos went on top of him and put a gun on his mouth angered by his actions. Vic managed to pull him off as they took care of the family.
Back at the Barn they wondered what would happen to the shop owners. Raoul Jimenez assured them that they wouldn't spend one day in jail, but Vic reminded him that they conspired to commit murder. Carlos then left and Vic offered him a ride, but he politely refused it.