A Chicago man is facing charges for robbing and assaulting two U.S. Postal Service carriers last year in suburban Forest Park.Devan Flax, 21, is accused of assaulting two mail carriers Nov. 25 and Nov. 28 before taking their U.S. Postal Service key, the Illinois attorney general’s office said. Flax was allegedly armed with a gun during both robberies.“U.S. Postal Service employees delivering mail to the American people must be allowed to do so safely and securely,” acting U.S. attorney Morris Pasqual said in a statement. “Individuals who use violence against postal carriers to gain access to the public's mail must be held accountable.”Flax was also charged with robbing a pizzeria in suburban Berwyn Nov. 26., officials said.Flax pleaded not guilty to assault, robbery and firearm charges at an arraignment last Wednesday.He is expected to appear in court Nov. 20.