Former Madison Police Department Officer Andrew Pullum pleaded guilty Monday to stealing nearly $4,000 during an anti-corruption sting operation, according to a Department of Justice release.

Pullum stole the money while under investigation by MPD, the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

MPD officer arrested for government theft in anticorruption sting

During the sting operation, which took place Dec. 17, 2015, an undercover officer posed as a girlfriend angry at her drug-dealing boyfriend and told Pullum about a car that may contain cocaine, according to the release. During the mock scenario, Pullum was presented with the opportunity to take $3,950 from the trunk of the car. Police watched from a plane equipped with infrared cameras.

Pullum took the bag of money from the trunk of the car, failed to turn it over to police and failed to log the money as evidence. Pullum did, however, call for a drug detection canine to assist in a search of the car.

Pullum was arrested on Dec. 18, 2015. The majority of the money that was stolen was recovered during a search of Pullum’s home after his arrest.

The investigation started after MPD received a tip from a citizen that Pullum might be corrupt. Joel DeSpain, MPD spokesperson, said MPD responded immediately to the tip.

“As soon as we got a tip that there may be an officer doing illegal activities, we quickly turned it over to the FBI,” DeSpain said.

Madison police officer arrested in anti-corruption sting pleads not guilty to theft, drug possession

Pullum was also charged with possessing 20 firearms while being a marijuana and cocaine user, according to the Wisconsin State Journal. Under the plea, prosecutors will dismiss that charge during his sentencing.

Pullum’s sentencing is scheduled for Aug. 23. Pullum faces a maximum of 10 years in federal prison.