In "Chasing Monsters", he had a one-night stand with a visiting detective from El Salvador, Detective Marcella Gomez, after the two had mutual understanding that they separately are divorced. Kim grew suspicious of her but Antonio doesn't believe her. Antonio asks Marcella about talking to a detective in the gang unit and she is honest about it. Kim, on the other hand, meets with Detective Keith O'Brien feeling she isn't getting the whole story. He tells a totally different story saying Marcella called him 2 months ago about El Lobo, not just the day before. When Antonio comes into the Squad room, Kim reveals everything they know about Marcella Gomez. Antonio is in total shock then believes her. At a house where Marcella was held up, Antonio asks Marcella to put the gun down. Antonio says it isn't worth it. Voight asks her to give him the gun but she says her life has been over since he killed her son. She shoots El Lobo in the head and raises her gun at Antonio, who takes the shot and kills her. Kim checks on Antonio at the station, he apologizes, saying he was distracted and she is a good partner who was just looking out for him. Voight says she was on a mission and there was nothing he could have said that could have stopped her. The only thing that kept her going was that hate; he reminds Antonio that he did what he had to do. Antonio looks at her picture and throws it in the garbage saying he did what she wanted him to do.
