American detectives used social media to track a fugitive to Oaxaca, Mexico, 20 years after he allegedly shot a man dead outside an Ohio bar – and there learned that he’d picked up an unexpected new job, becoming a police officer himself.

Antonio “El Diablo” Riano, now 62, was charged with first-degree murder, arrested in Zapotitlan Palmas and handed over to U.S. Marshals in Mexico City on Thursday, the agency wrote in a news release.

Riano fled Ohio after allegedly shooting 25-year-old Benjamin Becarra on Dec. 19, 2004, outside the Roundhouse Bar in Hamilton, Ohio, about 30 miles north of Cincinnati.

Witnesses said Riano and Becarra got into an argument inside the bar – when the dispute moved outside, a security camera allegedly caught Riano fatally shooting the other man in the face.

OHIO MAN SENTENCED TO LIFE IN PRISON FOR MURDERING HIS 3 YOUNG SONS AT THEIR HOME

“When Riano was arrested in Mexico he was found to be working as a local police officer,” the U.S. Marshals office said. A photo snapped of the fugitive as he was taken into custody shows him wearing his police uniform. 

As the 62-year-old was taken into custody at the Cincinnati/Northern Kentucky International Airport, a reporter with WKRC-TV asked why he became a police officer. In Spanish, he replied that he “wanted to help the people of Mexico.” 

OHIO DETECTIVE BRINGS DOWN ‘LADYKILLER’ SHAWN GRATE WITH 33-HOUR INTERROGATION: ‘A HUNGER TO KILL’

When asked by the station if he had killed Becarra, he replied, “No, I did not.”

Obtaining an indictment for Riano was simple, police told the outlet – Butler County sheriff’s deputies said they found security footage of him buying bullets a few hours before the shooting at an area Walmart, and the murder weapon stashed under the floorboards in his Ohio home. 

“We had all the evidence we needed gathered,” Mark Henson, a detective who was on the case in 2004, told WKRC. “We already had a direct indictment against him. It was just a matter of waiting to find him.”

GEORGIA GIRL, 12, MISSING SINCE MAY, FOUND SAFE IN OHIO; SUSPECT ARRESTED

Henson said he tracked Riano to New Jersey, where he had a sister, before hearing that he’d fled to his hometown of Oaxaca. 

“Not going to lie, at that time I was wondering if we were ever going to see him again,” Henson told WKRC-TV.

Before his capture, Riano was on the Butler County Sheriff’s Office “Most Wanted” list, and was even profiled on an episode of “America’s Most Wanted.”

Authorities started “actively looking” for Riano in January of this year, according to Paul Newton, a former deputy on the case who currently works for the Butler County Prosecutor’s Office. 

They quickly stumbled upon his Facebook page, learning that he was now employed as a police officer with the Zapotitlan Palmas Police Department and living in Oaxaca.

“I’m like, ‘My God, there he is!’” Newton told WKRC. “A little bit grayer, a little bit older, but it was him.”

When he fled the country, Riano left a wife and three children behind in Ohio, WKRC reported. Becarra’s family has been notified of Riano’s arrest and extradition, according to the outlet.