A veteran U.S. Border Patrol agent was arrested over the weekend, suspected of being a serial killer responsible for the deaths of at least four women and the kidnapping of another in a two-week span.

Juan David Ortiz, 35, of Laredo, is charged with four counts of murder, aggravated assault with a deadly weapon, unlawful restraint with exposure to serious bodily injury and evading arrest or detention, according to Webb County jail records. His combined bail on the charges was set at $2.5 million.

Ortiz, a Border Patrol agent since 2009, worked in intelligence, authorities said. He was off-duty at the time of the killings.

Webb County Sheriff Martin Cuellar and District Attorney Isidro "Chillo" Alaniz held an impromptu joint news conference Saturday near the rural site where one victim's body was recovered. All four slain women, including a transgender woman, were shot in the head.

All five victims, including the kidnapped woman, were sex workers, authorities said. Officials said Monday that Ortiz targeted the victims because of their work. 

"We do consider this to be a serial killer," Alaniz said. "He meets the qualifications or definition of being a serial killer."

Law enforcement officers are pictured Saturday, Sept. 15, 2018, at the scene where the body of a woman was found near Interstate 35 north of Laredo, Texas. Juan David Ortiz, a U.S. Border Patrol agent, is suspected of the serial killings of four women and the assault of a fifth woman who escaped and notified authorities.

Credit: Danny Zaragoza/The Laredo Morning Times via AP

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Credit: Danny Zaragoza/The Laredo Morning Times via AP

Though the case remains under investigation, detectives believe Ortiz acted alone, Cuellar said.

The Laredo Morning Times reported that an arrest affidavit in the case alleged that Ortiz confessed to the killings, which began with Melissa Ramirez, 29, on Sept. 3. The court document indicated that Ortiz picked Ramirez up in Laredo and drove her outside the city limits.

When she got out of his truck to urinate, he shot her multiple times in the head. Her body was found the next day.

"I hurt a lot. All I want is justice," Ramirez's mother, Maria Cristina Benavides, told the Times. "I want that guy to die in jail for taking the life of my daughter."

Ramirez, who got caught up in drugs, is also survived by a 7-year-old daughter and a 3-year-old son. Benavides had been awarded custody of the children, but Ramirez stayed with them in Rio Bravo several nights a week.

"She loved her children and when she was here, she took good care of them," Benavides told the newspaper.

The second victim, Claudine Anne Luera, 42, was found clinging to life Thursday along the same stretch of rural road, about two miles from where Ramirez was found. Luera died later that day at a hospital, the Times reported.

The Washington Post reported that Ortiz told investigators Luera, a mother of five, accused him of being the last person to see Ramirez alive.

Luera's sister, Colette Mireles, described her as a "happy-go-lucky" girl growing up, the Times said. A free spirit, she, like, Ramirez, became an addict as an adult, Mireles said.

A GoFundMe page was set up by a friend of Luera's daughter to help pay for her funeral.

The case came to a head Friday night, when Ortiz picked up a third woman, whose name is being withheld to protect her identity. The Post reported that the woman went with Ortiz, who she knew only as David, to his home, where she spoke of Ramirez, who had been a friend of hers.

The woman told investigators that Ortiz reacted strangely to the discussion, making her so uneasy that she vomited in his front yard before they drove to a gas station. At the gas station, she continued talking about Ramirez’s slaying, at which time Ortiz pulled out a pistol and pointed it at her, Ortiz later told detectives.

As they struggled inside the truck, Ortiz grabbed the woman's shirt. She pulled away -- and out of her shirt, which allowed her to escape. She ran to another nearby gas station, where she found safety with a state trooper fueling up his patrol car, the Post reported.

"The evidence then collected by the law enforcement investigators indicates that there is probable cause to believe that this individual is responsible for this series of murders," Alaniz said during Saturday's news conference.

Ortiz was captured around 2:30 a.m. Saturday, hiding in the bed of a truck in a hotel parking lot, Alaniz said. In the five hours between the third victim’s escape and his capture, however, he killed two more women.

Watch Webb County officials speak Saturday about the arrest of Juan David Ortiz, a Border Patrol agent, in connection with the serial killings of four women.

Ortiz told detectives he picked up the first woman, identified as Jane Doe in the affidavit, and drove out of the city limits on Interstate 35, where he told her to get out of the truck, shot her multiple times in the head and left her to die.

The transgender woman, identified by investigators Monday as 28-year-old Humberto Ortiz, was next. Juan Ortiz told investigators he picked up the victim -- who, according to family and friends, went by the name Janelle -- along the same roadway as Jane Doe and drove to a spot on I-35 about 5 miles from where he'd left Jane Doe's body.

After shooting Janelle Ortiz once in the back of the head, Juan Ortiz hid the body behind gravel pits nearby, the Times reported.

Jane Doe’s body was discovered Friday night. Janelle Ortiz’s body was found Saturday after Juan Ortiz told investigators where to look, the Times reported.

Janelle Ortiz's mother, Elva, told KPRC in Houston that she did not think her child was the killer's final victim because news reports identified the victim as male. Now, she is preparing to travel to Laredo to make funeral arrangements.

"I want justice done," the distraught mother told the news station. "That is what I want: For that man to get justice, to get what he needs (and) deserves."

Juan Ortiz left cryptic messages for his family on Facebook after the third victim escaped and before he was captured, the Post reported. The messages seemed to indicate he may not have expected to live much longer. 

“To my wife and kids, I love u,” one message read. Another stated, “Doc Ortiz checks out.”

Alaniz told the Post that Ortiz, who was a U.S. Navy corpsman, went by "Doc" while in the service.

Cuellar said that the case was resolved through the cooperation of multiple agencies, including U.S. Customs and Border Protection.

Agency officials issued a statement regarding Ortiz’s arrest.

“While it is CBP policy to not comment on the details of an ongoing investigation, criminal action by our employees is not, and will not be tolerated,” Andrew Meehan, a spokesman for the agency, said in a statement obtained by the Post. “Our sincerest condolences go out to the victims’ family and friends.”

Webb County officials give an update Monday on the case against Juan David Ortiz.

The string of slayings shocked the community in Laredo, a border town situated on the north bank of the Rio Grande River, across the river from the Mexican city of Nuevo Laredo.

"Laredo's not the sleepy town that we all grew up in," Alaniz said Saturday. "These are crimes that are consistent with bigger cities -- Laredo is a big city. We're seeing more and more serious crimes, (so) it can happen."

Ortiz is the fourth Border Patrol agent arrested in Laredo so far this year, the San Antonio Express-News reported. David Villarreal, 32, was arrested April 6 on charges that he threatened to deport a woman unless she had sex with him.

Villarreal, who was arrested on suspicion of sexual assault, tampering with physical evidence and official oppression, claimed that the woman had become "affectionate" toward him and that the sex was consensual, the Express-News reported.

Three days after Villarreal’s arrest, a supervisory Border Patrol agent, Ronald Anthony Burgos-Aviles, reported finding the bodies of Grizelda Hernandez and her 1-year-old son, Dominic Alexander Hernandez, in the brush near a park in Laredo.

Investigators in the double homicide learned that Burgos-Aviles, 29, not only knew Hernandez, but that he was the father of her son. Identified as the prime suspect, was indicted in June on two counts of capital murder. He faces the death penalty, the Express-News said.

A third agent, 24-year-old Luis Enrique Aranda, was arrested in April on allegations that he pawned his government-issued night vision equipment and reported it to his supervisors as stolen. The newspaper reported that he was charged with felony theft.

Alaniz said Saturday that residents need to take precautions and watch out for one another.

"Report suspicious vehicles (and) suspicious behavior," he said. "Help each other out. Protect one another."