Gonzo was Tuco Salamanca's brother-in-law and one of his lieutenants.
Gonzo and No-Doze stood guard outside of Tuco's office. Jesse Pinkman and Skinny Pete arrived to arrange a deal with Tuco for a pound of crystal meth. Gonzo frisked Pete and found nothing, while No-Doze searched Jesse and found the pound on him. After No-Doze handed the pound back to Jesse, both he and Gonzo led Jesse and Pete to meet with Tuco. While Jesse tried to negotiate $35,000 for the pound, Tuco instead made clear that their arrangement was going to involve split profits. Jesse tried to steal back the meth and run, but Gonzo and No-Doze caught him and took him back to his seat. Tuco then proceeded to beat Jesse with a bag of money and remind him that he was the only one allowed to deal crystal in the South Valley.
Later, Walter White came to the office to meet with Tuco. After No-Doze roughly frisked Walt and found a pound of what appeared to be meth on him, he handed it to Gonzo, who in turn gave it to Tuco. While Tuco looked over the pound, Gonzo and No-Doze led Walt into his office to meet him. Introducing himself as Heisenberg, Walt demanded $50,000 from Tuco, who simply laughed him off and mockingly described Walt's plan as "brilliant". Gonzo echoed this sentiment. Walt however, quickly proved them wrong and picked up a piece of the "meth", asserting that it was not meth at all before throwing it to the floor and causing a large explosion in the office. While Tuco, Gonzo, and No-Doze were all reeling from the shock, Walt grabbed the bag of what turned out to be mercury fulminate and threatened the trio with it. Gonzo unholstered his Beretta 92FS, but Tuco ordered him to calm down. Tuco then gave Walt his money and the two arranged a deal for two more pounds of crystal the next week before Walt left the ransacked office ("Crazy Handful of Nothin'").
The following week, Gonzo drove Tuco and No-Doze to meet with Walt and Jesse at a junkyard somewhere outside of town, with Gonzo carrying the bag of money. While No-Doze found the newest batch to be light, Tuco paid Walt and Jesse $17,000, until Walt negotiated that he would have the full batch by the next week. Tuco gave Walt the entire cash amount and they ultimately agreed to four pounds for the next week. An aggravated Tuco then left with Gonzo and No-Doze.
The following week, Walt and Jesse brought four pounds of their new Blue Sky formula, which was a complete batch this time. Tuco then snorted some of the crystal and assured Walt and Jesse that they would make a lot of money together. However, the celebration was interrupted when No-Doze reminded the two about remembering who they were working for. However, Tuco took No-Doze's remark as being disrespectful towards Walt and Jesse, and ultimately came to the conclusion that No-Doze was both calling Tuco stupid and speaking for him. While both Walt and No-Doze tried to calm Tuco down, Tuco appeared to do so, but then beat No-Doze repeatedly until he started to bleed heavily. Walt moved to stop Tuco, but Gonzo held him back, shaking his head in shock. After Tuco beat No-Doze unconscious, he reminded Walt and Jesse to meet again next week. Gonzo then carried No-Doze's unconscious body into the back of Tuco's Escalade and they drove off ("A No-Rough-Stuff-Type Deal").
As Walt and Jesse were driving out of the junkyard, Gonzo drove back and blocked their exit. Jumping out of his car, Tuco dragged a comatose No-Doze out of the car and threw him to the ground, and then angrily yelled to Walt to help him. No-Doze started convulsing, and Tuco demanded to know what was wrong with him, screaming at No-Doze for not knowing how to take a beating. Gonzo reacted in shock to Tuco's fury, but Tuco ordered him to be quiet. Tuco then yelled at Walt and Jesse to give No-Doze CPR and then to breathe into his mouth, but No-Doze bled out and died before they could revive him. Tuco then started furiously kicking No-Doze's body. Lacking any remorse over just having brutally killed his employee, Tuco merely told Gonzo to hide the body. While Gonzo was hesitant at first, saying that it wasn't very Christian to leave No-Doze in the junkyard where he could be chewed on by buzzards and rats, he ultimately acquiesced and carried No-Doze's body out of view, hiding him under a car, and covering his body with a large piece of scrap metal. He and Tuco then left the junkyard while Walt and Jesse could only react in horror.
Later that same day, Gonzo attempted to move No-Doze's body to give him better treatment, but the stack of cars where No-Doze's body lie shifted and crushed Gonzo's arm, ultimately causing him to bleed out and die after an unknown period of time. Their bodies were later found that night by DEA Agents Hank Schrader and Steven Gomez along with the APD. Hank then took a photo of their bodies and sent it to Walt, who along with Jesse, suspected that Tuco had killed Gonzo in order to remove any witnesses to the murder of No-Doze. Hank then recognized the two as Tuco's henchmen, and then posed to get photos of him with their bodies.
After the DEA successfully tied Tuco to No-Doze's murder, this led them to raid a number of his organization's places of business and arrest several of his lieutenants. However, with Gonzo not answering Tuco's calls, Tuco suspected that he was a police informant and proceeded to kidnap Walt and Jesse in an attempt to take them to Mexico in order to cook for the Juarez Cartel ("Seven Thirty-Seven").
While at his Uncle Hector's house in the countryside with Walt and Jesse as hostages, Tuco made clear that he should never have trusted Gonzo and that despite treating him like a brother, that he should never have trusted the people he cared about. He then said that if he was able to, that he would kill Gonzo.
Photos of Gonzo later appeared on the news as the DEA and APD continued to look for Tuco ("Grilled").
Gonzo was more brawn than brains, and was really just at Tuco's side to make sure no one stepped out of line, which was fine with him. Even if Tuco got psychotic from time to time, Gonzo appeared to know how to handle him. Mostly, he simply shut up and did his job. However, Gonzo had been known to disagree with some of his boss's methods - particularly, hiding No-Doze's corpse and leaving it to the buzzards without giving it a proper burial, which he deemed, "not very Christian." However, he reluctantly went to clean up the bloody mess Tuco created, which ultimately led to his death in the junkyard.
- Gonzo's mugshot later appeared on the DEA's board during a meeting which Hank presided over. His photo, along with both Tuco's and No-Doze's, was crossed out with a large red 'X' to signify his death. Also on the board were the mugshots of Emilio Koyama and Domingo "Krazy-8" Molina, who both had large red question marks over them to signify their unknown whearabouts. ("Phoenix")