A gang member with an extensive criminal record was found with a loaded handgun during a traffic stop in Oak Park, police said.

Michael Robertson, 25, of Elmhurst, was charged with aggravated unlawful use of a weapon by a felon. He'd been a passenger in a Mazda Protégé that was stopped after speeding and weaving through traffic on Harlem Avenue on March 16.

During the stop, police saw Robertson motioning toward his waistband, then asked him to get out of the car. He refused to answer any questions, turned away from officers and would not take his hand away from his right hip, River Forest Deputy Chief Craig Rutz said.

A pat-down revealed a Springfield Armory XD pistol with 16 rounds on his hip. Officers disarmed Robertson and took him into custody. In addition to the handgun, he was carrying a switchblade.

Robertson, a tattooed, admitted member of the Maniac Latin Disciples gang, had already endeared himself to local law enforcement officers after he spat on and assaulted a Metra employee in Aug. 2011, when he was busted for trying to ditch his train fare. After that incident, he was charged with three counts of felony aggravated battery to transit employees and one count of theft of services in River Forest.

Robertson remains in Cook County Jail in lieu of posting a $100,000, set at a bond hearing March 17. He was due to appear Monday in Maybrook Court.