A 10- year veteran United States Border Patrol supervisory agent was arrested Saturday, Sept. 15, in the deaths of four women—one of whom is transgender—and the aggravated assault of a fifth victim who narrowly escaped harm and alerted a police officer.

A spokesperson for Webb County Texas District Attorney Isidro R. “Chilo” Alaniz, told the Los Angeles Blade Monday that Juan David Ortiz, 35, confessed to killing four people between September 3 and September 15.

In the criminal affidavit filed by investigators from the Webb County Sheriff’s Office, the break in the case came Friday after a woman narrowly escaped Ortiz.

That woman, identified as Erika Pena, was sitting in a truck with a man named “David” and the two started talking about one of the prostitutes who had gone missing a week earlier. The man then pulled out a pistol and pointed it at her. When she tried to flee, he grabbed her shirt to prevent her from leaving the vehicle. Pena pulled off her shirt and ran to a nearby gas station where she encountered a Texas state trooper. She was able to provide a detailed description of Ortiz, according to affidavit.

Webb County Sheriff’s spokesperson Eduardo Chapa told the LA Blade, as well as other media outlets, that the bodies of four victims were found over the past two weeks. He added that homicide investigators were not ruling out the possibility of more victims.

An affidavit originally described the victims as three women and one man—but Chapa noted that the victim identified as male was, in fact, a transgender woman.

In a news conference posted to NBC Laredo affiliate KGNS’s Facebook page, Webb County Sheriff Martin Cuellar told reporters: “We have very strong evidence that he is the person who has been killing.”

According to the criminal complaint filed by Cuellar’s office, authorities found Ortiz at a gas station in Laredo, about 160 miles southwest of San Antonio. He fled the scene on foot and ran to a Ramada Inn where he was found hiding in the bed of a pickup truck, Alaniz said.

Ortiz was read his Miranda Rights and then he verbally confessed to killing four people over the last two weeks, the affidavit states. Two of the four killings took place in the hours after the woman was able to escape but before police tracked him down.

DA Alaniz, told the Associated Press Saturday that investigators “consider this to be a serial killer” whose victims were believed to be prostitutes. Alaniz described how the Customs and Border Patrol (CBP) supervisor continued going to work as usual throughout that time. “As law enforcement was looking for the killer,” he said, “[Ortiz ] would be reporting to work every day like normal.”

The killing spree became known to authorities with the discovery Sept. 4 of the body of 29-year-old Melissa Ramirez. According to the police affidavit, Ortiz said he killed Ramirez a day earlier. Like the other victims, Ramirez was shot in the head and left in a road in rural northwest Webb County. She was a mother of two.

A second victim, 42-year-old Claudine Anne Luera, was found shot and left in the road Thursday morning, badly injured but still alive, according to the affidavit. The mother of five died at a hospital later that day.

Authorities told the LA Blade Monday that Ortiz told investigators that after the victim escaped from his truck and ran off, he picked up his last two victims, whose identities have not yet been released and one of whom, Sheriff’s spokesperson Chapa confirmed, was the transgender woman.

A spokesperson for the U.S. Border Patrol told the LA Blade that the agency was cooperating with Sheriff’s investigators and the District Attorney’s Office.

“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. Out of respect to the victims’ family (sic), we ask that deference and due process be given to the investigation so that all the facts are brought to light and they can receive the closure they deserve,” the spokesperson said.

Reporting by The Associated Press, CNN, The Chicago Tribune, the staff of the Los Angeles Blade and wire service reports.