Dozens of family members and friends of four women who authorities say were killed by a U.S. Border Patrol agent gather for a candlelight vigil at a park in downtown Laredo, Texas, Sept. 18, 2018. Credit: Susan Montoya Bryan | AP

Prosecutors in Texas said that they would seek the death penalty for a U.S. Border Patrol agent accused of killing four sex workers in the region around Laredo, Texas, after he was indicted by a grand jury for capital murder Wednesday.

Juan David Ortiz, a 10-year veteran of the agency who worked in intelligence, was arrested in September and charged with four counts of murder. But the grand jury upgraded the charges against him.

Ortiz picked up the victims from the side of the road on separate occasions in early September, according to prosecutors. Officials have identified the victims as Melissa Ramirez, 29; Claudine Ann Luera, 42; Griselda Alicia Hernandez Cantu, 35; and Nikki Enriquez, 28, a transgender woman.

All were killed or left for dead in rural parts of Webb County, which borders the Rio Grande River, the dividing line between the United States and Mexico. Laredo is about 150 miles southwest of San Antonio.

Webb County District Attorney Isidro Alaniz told reporters Wednesday that Cantu survived being shot twice in the neck only to be killed by blunt-force injuries. He said the death penalty was warranted because of the horrific nature of the crimes.

“The horrific nature of the murders. His complete disregard for human life. His vigilante mentality. He violated his oath to his country and his agency that he swore to protect,” Alaniz said. “We also believe that there are no mitigating circumstances in his life where it is justified for life without parole.”

Alaniz said that Ortiz had told investigators that his goal had been to “clean up the streets of Laredo by targeting this community of individuals who he perceived to be disposable.”

“The evidence that was presented to the grand jury this morning showed that he killed these four innocent individuals in a cold, callous and calculated way,” he said.

Ortiz has been suspended without pay since his arrest, U.S. Customs and Border Protection spokesman Carlos Diaz said.

“CBP will continue to support other law enforcement agencies conducting the investigation related to this case,” a statement Diaz sent said.

Earlier in the case, Webb County Sheriff Martin Cuellar said he believed Ortiz, who lived with a wife and two children, was a serial killer.

Ortiz was arrested after a woman had escaped from his truck and alerted authorities when he pulled a gun on her, officials said. He has been held on a $2.5 million bond since.

Alaniz told USA Today that police found .40-caliber casings at the scene of the killings, which would be consistent with the .40-caliber HK P2000 pistol Ortiz had been issued by the Border Patrol.

Arrest records recount the brutal execution-style killings, along with the alarm that spread within the seemingly tightknit community of sex workers after the first two slayings.

Ortiz told investigators that he picked up Ramirez on Sept. 3. They drove about 30 miles from town, and she got out of his vehicle to urinate near a country road cutting through dense shrub land.

Then he shot her in the head multiple times, the affidavit says. She was later found dead. Ramirez was a mother of two young children, the Laredo Morning Times reported.

“I hurt a lot. All I want is justice. I want that guy to die in jail for taking the life of my daughter,” her mother, Maria Cristina Benavides, told the paper.

Ten days later, investigators said, Ortiz drove Luera outside the city a few miles from where he said he killed Ramirez.

He told investigators that she accused him of being the last person to see Ramirez alive.

Ortiz said she got out and that he shot her in the head, the document says. Luera was found alive but died of her wounds at a hospital.

The next two killings occurred in the hours after the woman escaped early Saturday, authorities said.