SALEM – A leading member of a notorious Lynn gang already serving 15 years in federal prison for conspiracy to sell crack cocaine received another 10-year prison term for robbery, cocaine trafficking and firearm charges in Superior Court.Donald Oliver, Jr., 23, of 85 Timson St., Lynn, changed his plea to guilty Tuesday afternoon on charges of armed robbery, a felon in possession of a firearm, trafficking over 100 grams of cocaine and possession of ammunition involving two cases out of Lynn.Judge Howard J. Whitehead agreed to adopt the recommendation offered by prosecutors and defense.The sentence will run simultaneously with the federal term, instead of one after the other.On April 3, 2006, Oliver was arrested at an apartment at 25 Rogers Ave., with approximately 106 grams of cocaine and ammunition.Then while out on bail he was arrested March 1, 2007 after trying to sell two guns to a confidential informant, but when he met the informant, who was wired, in the rear of Lafayette Park to complete the transaction, he instead robbed a gold chain and money from him at gunpoint.The guns were recovered along with the gold chain when police arrested him later that day.The entire incident was videotaped and recorded by police.Last month Oliver was sentenced to 15 years in federal prison for conspiracy to sell crack cocaine.Oliver was indicted by federal authorities along with 16 other members of the Deuce Boyz and Soldiers gangs a year ago in a local, state and federal gang crackdown.Oliver was apparently named as “a leader of the Deuce Boyz/Soldiers” in an FBI court affidavit.