Laredo, TX – A U.S. Border Patrol Agent has confessed to the murders of four women, and a failed attempt at a fifth, in a brutal crime spree that began Sept. 3.

A supervisory Border Patrol agent named Juan David Ortiz was arrested at about 2:30 a.m. on Saturday after a woman who barely escaped being his next victim ran up to a state trooper at a gas station and asked for help, The Washington Post reported.

Webb County District Attorney Isidro Alaniz said Ortiz committed the murders when he was off-duty and using his personal vehicle, a four-door white Dodge pickup truck, according to Newsweek.

"As law enforcement was looking for the killer… he would be reporting to work every day like normal," Alaniz said.

He told reporters that he believed the murders were acts committed by a “serial killer” after two women who were believed to be prostitutes had been found murdered in the Laredo area in September, Newsweek reported.

When police found Ortiz, 35, hiding in his truck in a hotel parking lot early on Saturday morning, he confessed to two murders and told officers that he had murdered two more women in the hours since the one victim escaped, according to The Washington Post.

Ortiz told detectives that he had picked up his first victim, 29-year-old Melissa Ramirez, on Sept. 3 and driven about 30 miles outside of town with her.

Then Ramirez got out of the truck to go to the bathroom, and Ortiz shot her multiple times in the head, according to the arrest affidavit.

Ortiz said he picked up his second victim, 42-year-old Claudine Ann Luera, on September 13 and drove out of town with her, to a spot not far from where he killed Ramirez, The Washington Post reported.

The affidavit said Ortiz told police that Luera accused him of having been the last person to see Ramirez alive.

When she got of the car, Ortiz shot her in the head and left her for dead.

The affidavit said Luera “was found shot and left in the road Thursday morning, badly injured but still alive,” Newsweek reported. The mother of five died at the hospital later the same day.

Ortiz picked up the victim who actually escaped on Sept. 14, and took her back to his house.

The victim told police that she’d brought up the subject of Ramirez’s death and Ortiz had reacted strangely, The Washington Post reported.

She said they left to go to a gas station and she brought up the topic of Ramirez’s murder again, and then Ortiz pulled out a gun and grabbed her shirt.

The woman managed to escape, jumping out of the truck and tearing her shirt off in the process, according to The Washington Post.

Ortiz fled in his truck, and the woman ran for help to a nearby gas station, where she found a Texas state trooper getting gas, and went to him for help.

In his report, the trooper described being approached by a “shirtless adult female asking for help.”

In the time between when the woman escaped and when authorities found him a few hours later, Ortiz told police that he had killed two more women.

He also posted a series of cryptic messages on Facebook, The Washington Post reported.

“To my wife and kids, I love u,” one post read.

“Doc Ortiz checks out. Farewell,” Ortiz wrote in another post, referring to himself by his Navy corpsman nickname.

Alaniz told reporters that initially, Ortiz was uncooperative when investigators interviewed him. But then after they agreed to remove his handcuffs, he became more cooperative and started to offer details of his killing spree.

The district attorney said Ortiz talked of shooting one woman in the face, and another woman from his vehicle, without emotion or tears.

“This guy is cold,” Alaniz said.

Police have not released the names or details associated with the last two murders.

“We consider this man to be a serial killer who was preying on one victim after another,” Webb County Sheriff Martin Cuellar said.

Police said the victims were all killed or left for dead in rural parts of Webb County, which borders the Rio Grande, The Washington Post reported.

All of the victims were believed to have been sex workers and investigators said that there were indications that not all of the victims were chosen at random.

Ortiz’s first two victims were U.S. citizens, but police have not released those details about the other three women. The Associated Press reported that one of the last two women killed was transgender, according to Newsweek.

The investigation is being led by the Texas Rangers and the Webb County Sheriff’s Office, and Customs and Border Protection (CBP) was cooperating with investigators.

“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,” CBP Spokesman Andrew Meehan said in a written statement. “Our sincerest condolences go out to the victims’ family and friends.”

Alaniz said investigators believe Ortiz, who is a 10-year veteran of the Border Patrol who worked in intelligence, committed the murders alone.

The district attorney told The Washington Post that Ortiz has been charged with four counts of murder, aggravated assault, and unlawful restraint. He was being held on a $2.5 million bond.

Ortiz is not the only Laredo Sector Border Patrol supervisor who has been arrested for multiple murders this year.

Police arrested 29-year-old Ronald Anthony Burgos-Aviles on April 9 for the fatal stabbings of his lover and their one-year-old child, the Laredo Morning Times reported.

Burgos-Aviles is accused of having pretended to discover the bodies of Grizelda Hernandez and her one-year-old son Dominic Alexander Hernandez in a park near the United States – Mexico border.

However, investigators quickly determined that the Border Patrol agent had a romantic relationship with Hernandez, and that her little boy was the biological son of Burgos-Aviles, KGNS reported.