0249 GMT September 23, 2018
Officers began looking for Juan David Ortiz in the city of Laredo after a fifth woman allegedly escaped from him and got help from local police, BBC reported.
Ortiz, who has worked for the force for a decade, initially fled but was later arrested in a hotel parking lot.
The names of the four victims have not been revealed.
Webb County Sheriff Martin Cuellar said police believed Ortiz had acted alone.
"The county, the city can rest assured we have the serial killer in custody," Sheriff Cuellar said, in quotes reported by the Laredo Times newspaper.
Two of the victims were found earlier this month in a rural area by the Interstate 35 road, and the third and fourth victims were found in the same area in recent days, according to local reports.
A 42-year-old woman had been found injured on Thursday but died in hospital.
District Attorney Isidro Alaniz described the killings as a ‘horrific case’ and confirmed Ortiz was set to face four charges of murder and one of aggravated kidnapping.
He said the cause of death was similar for all four women who, authorities believe, were killed over two weeks.
He said the investigators were trying to find a motive for the killings.
Two of the victims were US citizens, he added. Few other details have been released.
The Texas Tribune reported the fifth woman fled from a petrol station after Ortiz allegedly pointed a gun at her when she tried to get out of his vehicle.
Andrew Meehan, assistant commissioner for public affairs for US Customs and Border Protection, confirmed in a statement that the agency was cooperating with police.
"Our sincerest condolences go out to the victims' family and friends," he said.