A Dallas police officer has been taken into custody in connection with two murders.

The Associated Press reports that Bryan Riser was arrested on two counts of capital murder after a man came forward in August 2019 and told authorities that he had helped Riser kidnap and murder two people. The man said Riser instructed him to murder 31-year-old Liza Saenz and 61-year-old Albert Douglas in 2017, in two unconnected killings. Police apprehended Riser—who has been on the force for 13 years—on Thursday morning and took him to the Dallas County Jail.

During a news conference, police Chief Eddie Garcia said Riser’s motive is unknown, and it wasn’t tied to his police work. Garcia didn’t divulge why it took so long to arrest Riser after the man who committed the killings came forward. The homicide division and FBI are currently investigating.

Saenz's body was discovered in the Trinity River on March 10, 2017 with a number of bullet wounds. Douglas went missing that year but hasn’t yet been found. It’s unclear if the man who committed the murders has been charged.

Riser became a cop in 2008 and served as a patrol officer up until his arrest. Garcia said Riser was still actively patrolling Dallas as he was being investigated. He’s since been placed on administrative leave while an internal affairs inquiry proceeds.

“We’re going to expedite our process so this individual is no longer with the department,” Garcia said. “We will not allow anyone to tarnish this badge.”