A Palatka police detective who ran for Putnam County sheriff was arrested during a St. Johns County weekend prostitution sting and has resigned, authorities said.

Reno Fells, 48, resigned from the department Sunday, said Assistant Chief James Griffith of the Palatka Police Department.

Fells had been a commander with the department then resigned to run in the 2012 sheriff's race, then returned to the department as a detective, Griffith said. Fells was defeated in the 2012 Democratic primary.

Griffith received a call from Fells about the arrest early Saturday, within six hours of the arrest.

He was arrested Friday, said Cmdr. Chuck Mulligan of the St. Johns County Sheriff's Office.

Operation Summer Lovin' was a four-day prostitution sting run in conjunction with the St. Augustine Beach Police Department. A briefing on the arrests is scheduled for 1:30 p.m. Monday.

Fells began his career as a school resource and corrections officer for the Putnam Sheriff's Office in 1988 . In 1997 he started with Palatka police and rose to operations commander. He resigned to run for sheriff in 2011 and was rehired in December 2013 as a detective.