CHICAGO (WLS) -- A former Cook County Sheriff's Department officer has pleaded guilty to robbing drug dealers and re-selling their drugs to make a profit, officials said.Robert Vaughan, 44, admitted that he robbed eight drug dealers between 2011 and 2013 along with two other law enforcement officers while on duty, according to his written plea agreement. The trio shared a total profit of $300,000 during that time.Vaughan admitted to conducting deals with dealers; after the transactions, he would arrest and handcuff the individuals but keep the narcotics for himself and release the dealers without charges, according to the plea. Vaughan later sold the narcotics to other traffickers to make a profit.His plea agreement says the robberies, which included marijuana, cocaine and contraband cigarettes, were carried out in Chicago, Cicero, Plainfield, Lyons, Melrose Park and Forest Park.He was taken into custody on Nov. 3, 2014, after he and another officer robbed an undercover federal agent of 70 pounds of marijuana. He faces one count of robbery - a maximum sentence of 20 years in prison plus a maximum fine of $250,000.