Juan David Ortiz has been charged with four counts of murder, aggravated assault and unlawful restraint, according to Web County District Attorney Isidro Alaniz.
Mr Ortiz was arrested on Saturday in Laredo, Texas, a city on the Mexican border. His bail has been set at $US2.5 million ($A3.5 million).
Police believe the suspect is behind the killing of four women since September 3. Mr Alaniz confirmed to The Texas Tribune all of the women were sex workers and one was a transgender woman.
Mr Alaniz said he believed the four deaths were the work of a serial killer.
“The manner in which they were killed is similar in all the cases from the evidence,” he said.
Webb County Sheriff Martin Cuellar said investigators had “very strong evidence” to tie Mr Ortiz to the murders.
A motive for the killings was not clear and authorities are still investigating, however it is believed the killer acted alone. Originally authorities would not reveal how two of the victims women were killed but recent reports say the first two were shot in the head and left on the road.
Mr Ortiz was arrested after a woman named Erika Pena realised she was in danger and managed to flee and run to a petrol station, at which point she was able to alert a state trooper.
The first victim was mum-of-two Melissa Ramirez, 29. Her body was found on Tuesday, September 4.
In a police affidavit, Mr Ortiz said he killed Ms Ramirez the day before her body was found.
The second victim, Claudine Anne Luera, 42, was shot and left on the road on Thursday morning. Badly injured but still alive, she died at the hospital a day later.
According to the affidavit, Mr Ortiz told investigators he picked up the last two victims after Ms Pena escaped. The identities of the women have not yet been made public.
Ortiz worked as a supervisor of the United States Border Force. He had been with the federal agency for 10 years and went to work every day as normal during the killing spree.
“It’s interesting that he would be observing and watching as law enforcement was looking for the killer, that he would be reporting to work every day like normal,” Mr Alaniz said.
Sheriff Cuellar expressed his condolences to the families of the victims.
“Our Webb County Sheriff’s Office team of investigators, together with the Department of Public Safety, the Texas Rangers and the District Attorney’s Office, have been working diligently on this case,” he said.
The US Border Force has also issued a statement offering “sincerest condolences” to the victims’ families.
— with wires