A U.S. Border Patrol agent is suspected of being a serial killer after he was arrested on suspicion of kidnapping in rural Webb County, Texas, authorities announced Saturday.

Webb County Sheriff Martin Cuellar said at a news conference that Juan David Ortiz was booked Saturday morning after a woman he allegedly attempted to kidnap Friday escaped and went to law enforcement. He said authorities believe Ortiz is behind the murder of four women in a nearly two-week span.

"We have very strong evidence that he is the person that’s been killing," the sheriff said.

Starting nearly two weeks ago, local investigators were trying to find a killer of women whose bodies were found in the border county that abuts the Rio Grande.

A woman described by authorities as a "second victim" was found Thursday "with head trauma injury" off state highway 255, according to a statement from Texas Rangers. She was identified as Claudine Anne Luera, 42, of Laredo, Texas.

A third body was found Saturday morning, then a fourth was found just after noon along the a highway north of Laredo, NBC News affiliate KGNS reported.

Details on the other victims weren't immediately available from a Rangers spokesman.

The women were sex workers whom the agent had allegedly "picked up," KGNS reported, citing Webb County District Attorney Isidro Alaniz. Officials don't believe there are other victims.

It's not clear if they think the suspect was on-duty at the time of the alleged killings.

U.S. Customs and Border Protection assistant commissioner for public affairs Andrew Meehan said in a statement that Ortiz is a supervisory agent. "There are charges pending related to multiple homicides in the Laredo area," he said.

He did not discuss if the agency has taken disciplinary action but said CBP's Office of Professional Responsibility 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," Meehan said.

NBC News reached out to the Webb County public defender's office and did not get a response on whether Ortiz has legal representation.

Cuellar said Ortiz is a 10-year veteran with Border Patrol. He was detained overnight Friday before being formally arrested in connection with the alleged kidnapping, the sheriff, speaking at a news conference, said.

District Attorney Alaniz told reporters, "There is probable cause that this individual is responsible for this series of murders which qualify as a serial murder [case]."

Jail records show he was charged with four counts of murder, aggravated assault with a deadly weapon and other crimes. He was being held in lieu of $2.5 million bond.

The investigation was undertaken jointly by the Rangers and the Webb County Sheriff's Office, said Rangers Staff Sgt. Erick Estrada.