- "Nick. There was a boy no older than you. He lived in these streets. An addict. And he tried to steal from me many times. When the world changed, this boy got his hands on something. Something mean. To this day I have no idea what drug he took, but he was mistaken for a sombra. A mob attacked him, herded him with the other infected. They were killing them. So I rushed in, I tried to save him. There were limbs, jaws, blood. It was chaos. And in this moment as I was beaten by the living, I was bitten by the dead. A hand found me and I saw Luciana. She brought me back here. We waited for death to come. "
- —Alejando to Nick Clark about how he was bitten and saved by Luciana Galvez[src]
Tijuana, Baja California
Nothing is known about Alejandro's life before the outbreak, except that he lived in Tijuana, Baja California, and was a pharmacist.
Alejandro is first encountered in the survivor community of La Colonia, where he meets Nick and has a chat with him as he tends to injured leg. He then welcomes him to the community, revealing children playing soccer and other survivors trading at the shop stalls.
Alejandro is first seen with Luciana and Alonso, one of the residents of the community. The dying neighbor offers up his knife and hugs Luciana before entering through a bus that leads to a fenced off area of the community full of the Infected. Alejandro and the rest of the community watch on and chant as the man is devoured.
Alejandro is later seen attending an old man's leg, injecting it with medicine. Oliviero requests to not be given any more treatment as he is dying and the Colonia's supplies would be allocated better to the other members, wishing to join the wall of Infected. Alejandro complies but states he will still attend him in that moment. Nick looks onward as Alejandro converses with Luciana afterwards.
Alejandro then requests a meeting with Nick after the latter had returned with Luciana from his errand of gathering supplies from Marco's gang. There he reprimands Nick for his reckless action of stealing a pastry for the orphan daughter of the devoured man, potentially putting the community at risk. Nick defends himself by saying the girl deserved comfort for the loss of her father.
The pair then discuss their differing opinions on the wall of Infected and the belief of the dead walking towards their "final resting place". Alejandro then reveals to Nick that his earlier attention to Oliviero was a ruse in order to keep hope alive as they are slowly running out of medicine. As Alejandro reaches for a bottle of water, Nick notes a bite mark on his left shoulder and recognizes it as the walker bite Luciana mentioned that he supposedly survived from. Before Nick leaves, Alejandro coldly threatens Nick that he will feed him to the wall should he put the Colonia in potential danger again.
Alejandro is latter seen preaching to his community with Nick among them.
Alejandro is upstairs in his pharmacy as patients and volunteers fill the clinic downstairs. Alejandro is approached by Nick with a desire to help La Colonia and the situation with Marco's gang. He shows Alejandro his way of increasing their Oxy supply while duping the gang without them knowing it. Alejandro eventually warms up to Nick and applauds his skill. He then takes Nick outside and shares the story of how he was bitten as he tried to save a young addict after he was thrown to "the wall" by terrified neighbors. He stated that he tried to save the addict as the dead swarmed them and the neighbors beat them, but he was unsuccessful. However, he was saved by Luciana and brought back to the pharmacy to die, but he healed from his supposed zombie bite. In the marketplace, Alejandro and Nick happily watch a children's soccer game until Francisco returns from a run and informs Alejandro that Pablo was found "in pieces".
Later that day, Alejandro thanks Nick for making the run to the supermarket to hand off the Oxy to Marco's gang. As a way of thanks for all of Nick's help, Alejandro decides to give Nick one of the vacant homes in La Colonia.
Alejandro is informed by Nick and Luciana that Francisco left La Colonia. "No thank you, no goodbye," Alejandro says bitterly. He asks Luciana to speak with the scouts to boost morale in the wake of Francisco's departure. Alejandro addresses his people at the church and urges them to keep their faith in him and in the safety of their home. Afterwards, he questions Luciana's loyalty for neglecting to speak with the scouts immediately. He forbids her and Nick from doing the drug trade, despite Nick's fears that Marco will come for them if he doesn't receive his supplies.
At the infirmary, Nick and Luciana brief Alejandro on Marco's impending assault. Nick urges Alejandro to vacate La Colonia immediately. The debate is interrupted by a patient who has turned. The infected attacks and, in the ensuing scuffle, Alejandro and two others are bitten. Nick kills the infected by pressing his fingers through the eyeballs, into the brain. Alejandro gapes at the bite on his arm, but he assures Nick and Luciana that he will be fine.
The La Colonia townspeople say farewell as the infected infirmary victims offer themselves up to the herd in the yard. Nick tells Luciana he's worried about Alejandro. She assures him that Alejandro's faith will heal him.
Nick packs a bag in his trailer and tells Luciana they must leave, refusing to believe that faith will protect them from Marco's gang. Alejandro stops by. Nick orders Alejandro to tell Luciana his secret. Alejandro admits that he is not immune to infected bites, explaining that the bite on his neck actually came from the boy he was trying to save, not from an infected. Luciana reels from the news. Nick begs Luciana to come with him. She refuses, saying La Colonia is her home.
Luciana dresses Alejandro's bite wound. He tells her he's dying. She orders him to lie to the townspeople to keep their faith intact. Alejandro accepts and he warns the townspeople that men are coming to kill them, but that their faith will protect them. "We will not die today," he declares. Nick returns to La Colonia and goes to Alejandro in his trailer. Nick says he saw a medevac helicopter land in a camp near the border and urges Alejandro to give the villagers permission to flee. Nick says he and Luciana can lead the villagers north. The next day, Marco and the Los Hermanos gangsters arrive at La Colonia and shoot infected in the fenced yard before entering the premises.
Marco's gang finds the town deserted and celebrates their easy victory. Alejandro watches from a hiding spot then goes to the school bus in the yard. He starts the bus. Marco hears the bus and runs toward the yard.
Alejandro drives the bus forward, unblocking the fence gap and allowing the infected to flood into La Colonia. Marco's gang sees the herd walking toward them and runs.
Madison and Travis find Alicia on the bus, tending to a dying Alejandro. Madison tells Alejandro she's looking for Nick. Alejandro informs Madison that Nick went to the border because he saw something, but dies before he can mention the camp. Then, Alicia hands Madison her Balisong. Madison closes Alejandro's eyes, turns his head to the side, and drives in the blade, preventing him from reanimating.
Alejandro is bitten by an infected, but keeps the fact that he's dying from the residents of La Colonia. Alejandro eventually succumbs to his infection before Madison Clark stabs him in the head to prevent reanimation.
This list shows the victims Alejandro has killed:
- Marco Rodriguez (Caused)
- Antonio Reyes (Caused)
- Ramiro (Caused)
- At least 22 members of the Los Hermanos (Caused)
- Numerous counts of zombies
- Alejandro's last name was revealed in dialogue with Oliverio in "Los Muertos", he was referred to as Dr. Nuñez.
- Alejandro was supposedly the only character in the entire Walking Dead universe known to survive a walker bite without having his limbs amputated (and amputation would be impossible due to that he was bitten on the shoulder), but in Wrath it was confirmed that he lied about his bite wound and he was actually bitten by the junkie he attempted to rescue.
- The casting call for this character used the name Antonio Martinez.
- He was described as "Latino. Mid 40s-50s. A man with the mannerisms of both a doctor and a preacher, he is unassuming but has a strong presence - a sense of gravitas and command. He says a lot with very few words".