(CNN) A South Texas Border Patrol agent who confessed to fatally shooting four women was indicted Wednesday on a charge of capital murder, with the local prosecutor vowing to seek the death penalty.

Juan David Ortiz, 35, confessed to the killings committed during the first two weeks of September in and around the border town of Laredo. He was arrested in September 15, hours after another would-be victim, Erika Peña, escaped.

Webb County District Attorney District Attorney Isidro Alaniz, at Wednesday news conference, described Ortiz as a self-proclaimed vigilante who wanted to "clean up the streets of Laredo by targeting individuals he deemed to be disposable and that no one would care about. People he did not give value to."

"In this case," Alaniz said, "he preyed on the weak, the sick and the vulnerable."

A county grand jury returned the indictment on the federal murder charge Wednesday, according to Alaniz. He was also indicted on one count of aggravated assault with a deadly weapon, one count of unlawful restraint with reckless exposure to serious bodily injury and evading arrest or detention.

Alaniz said the Texas Penal code allows a lone capital murder count if the defendant carried out multiple murders "pursuant to the same scheme or course of conduct."

"Ortiz, by day, he was a family man," the prosecutor told reporters. "The evidence shows that he was a supervisor. That he would go about his daily activities like anybody here. He appeared normal by all accounts and circumstances. At the nighttime, he was someone else, hunting the streets of San Bernardo for this community of people and arbitrarily deciding who he was going to kill next."

Ortiz, a 10-year veteran of US Customs and Border Protection, was originally charged with four counts of first-degree murder.

There was no immediate comment from an attorney for Ortiz.

His bond was set at 2.5 million dollars. Capital murder is punishable by death or life in prison without the possibility of parole.

Ortiz, a supervisory Border Patrol agent with access to US Customs and Border Protection intelligence, had been holding Peña at gunpoint, but she got away away and ran to a state trooper who was fueling up at a nearby gas station.

An unlikely escape, a surprising arrest

Peña's family says it's a miracle she's alive. Now, she's considered the hero who brought down the alleged serial killer.

Ortiz allegedly picked Peña up at a prostitution hub on September 14. Peña knew Ortiz as "David," and rode with him to his home in the northern part of Laredo, the affidavit said. Peña noticed that Ortiz "began to act weird" when she brought up her acquaintance, Melissa Ramirez, who had been killed the week before, according to the affidavit.

From his home, Ortiz took Peña to a gas station off the Texas 20 Loop, and there they again discussed Ramirez, police say.

That's when Ortiz pulled out a pistol and pointed it at Peña, according to the affidavit. Ortiz grabbed her shirt to prevent a screaming Peña from leaving the car, the affidavit says.

Peña maneuvered herself out of her top to escape him, according to the affidavit, and as she ran to a state trooper fueling up at the gas station, Ortiz drove away.

Peña was able to describe Ortiz, his tattoos and his truck, as well as bring investigators to his home, the affidavit says.

Just after midnight, police issued an alert for law enforcement to be on the lookout for Ortiz, and at about 1 a.m., they spotted him at a gas station. Ortiz fled, according to police.

They found him about an hour and a half later, hiding in the bed of a truck in the parking garage of a Ramada Inn, Alaniz said.

The victims

When police brought Ortiz in, they say he confessed -- to an additional four murders.

Two took place after Peña's escape.

His first victim, police say, was 29-year-old Melissa Ramirez. Ortiz told police he picked her up September 3 and drove her out to the edge of the city, where she exited his vehicle to urinate on the side of the road, the affidavit says. Ortiz shot her multiple times in the back of the head and drove away, according to police.

On the Thursday before Peña's escape, Ortiz picked up another woman -- 42-year-old Claudine Ann Luera -- and drove her outside of Laredo. After she became suspicious and accused Ortiz of being the last person seen with Ramirez, Luera got out of the vehicle, the affidavit says.

Ortiz shot her multiple times in the head and fled, police allege.

After Peña escaped Ortiz, the Border Patrol agent picked up another woman initially identified as Jane Doe. He ordered her out of the car and shot her repeatedly in the head, the affidavit says. She was later identified as Guiselda Alicia Cantu.

Later Saturday morning, Ortiz picked up a transgender woman and drove her about five miles from where he killed Jane Doe, the affidavit says. Police identified the transgender woman as Humberto Ortiz; later, the DA's office said she went by Janelle. CNN is attempting to confirm the victim's preferred name and pronoun.

He ordered her out of the car and shot her once in the back of the head, the affidavit says.

"The evidence that we have right now is that he committed these murders in a similar fashion, taking these individuals out to desolate areas, near or right outside the city limits, and executing them with a hand gun," Alaniz said.

Authorities said Ortiz preyed upon vulnerable victims in communities he disliked -- people who struggled with drug or alcohol addiction or were involved in sex work.

"The suspect was hunting for his victims," Alaniz said.

He got to know the people he targeted and met with them several times to gain their trust, according to Webb County Sheriff's Department Chief Deputy Federico Garza.