Webb County District Attorney Isidro Alaniz told reporters at a press conference following the arrest that Ortiz qualifies as a serial murder.
A border agent was arrested early Saturday in South Texas by officials searching for a serial killer in the Laredo area.
A fifth person, a female who was the victim in the alleged kidnapping, was able to escape and contacted authorities, providing a description of the suspect - including a vehicle, a white Dodge truck, authorities said. Sheriff Martin Cuellar said Ortiz fled from state troopers and was found hiding in the parking lot of a hotel in Laredo, a border city about 235 kilometres southwest of San Antonio. Cuellar said his department has "very strong evidence" to believe Ortiz killed the women, who he said were sex workers.
Andrew Meehan, a senior US Customs and Border Protection official, said in a statement that the agency was co-operating fully with investigators. Alaniz said two of them were USA citizens but the nationalities of the other two were not yet known.
Border Patrol agents are great men and women who work hard to keep us safe, and we thank them for their work.
All of these cases are related to the almost two week murder investigation of two other women who were found killed in a rural part of Webb County.
Ortiz, Cuellar said, spent 10 years as an agent with the US Border Patrol. Cuellar said investigators believe Ortiz acted alone.
The Texas Rangers, along with the Webb County Sheriff's office, launched an investigation after Melissa Ramirez, 29, a mother of two, was found slain September 4.
"I extend my condolences to the families of the victims during this hard time".
"The manner in which they were killed is similar in all the cases from the evidence", said Alaniz. But the spokesperson referred all other questions to authorities in Webb County and the Texas Department of Public Safety.