The deputy police chief of Fresno, California, and three other people were arrested Thursday on federal drug charges and accused of plotting to distribute oxycodone and heroin, authorities said. Deputy Police Chief Keith Foster, 51, is a 29-year-veteran of the Fresno Police Department and was in charge of patrol operations for four police districts.

Foster was arrested after a year-long joint investigation, conducted by the FBI and the ATF, including using wiretaps and surveillance. Foster has been put on emergency leave until the Fresno police department completes its internal investigation into the matter. Others arrested with Foster were Fresno residents Rafael Guzman, Jennifer Donebedian and Randy Flowers. 

"This is a very sad day for the Fresno Police Department, the citizens of Fresno, the law enforcement profession, and for me personally," Fresno Police Chief Jerry Dyer said, at a news conference on Thursday, according to the Associated Press (AP).

In one of the tapped phone calls, Foster had told Flowers that he had "100 of those things," U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives special agent Sherri L. Reynolds said in an affidavit, according to AP. Foster later reportedly picked up a prescription for 100 oxycodone tablets and later drove to Flowers' home. Foster was again found picking a prescription for oxycodone tablets and delivering them to Flowers, who has a long criminal history.

In 1988, he was convicted for possessing cocaine base for sale and, in 1994, he was convicted for being a felon and addict in possession of a firearm, AP reported, citing the affidavit. In 2002, he was convicted for delivering a schedule II controlled substance from Marion County, Oregon. In 2002, Flowers was interviewed by Action News, when Foster's nephew, Eric Foster, was shot and killed during an officer-involved incident.

"He was just an outgoing person. He had his things. But he wasn't a bad person," Flowers had said, according to ABC30.