A man who took part in a schoolyard ambush as a teen pleaded not guilty Wednesday to a new weapons charge.

Mitchell Johnson, 23, appeared before a federal magistrate on one count of possession of a firearm while either a user or addicted to a controlled substance, said Debbie Groom, a spokeswoman for the U.S. Attorney's Office in the Western District of Arkansas.

Police pulled over Johnson and another man in a traffic stop in January. Johnson was cited when authorities said he had marijuana and a firearm.

A state prosecutor later dropped the misdemeanor drug and weapon charges at the request of federal officials.

Johnson and Andrew Golden were convicted in juvenile court of the 1998 shootings of four classmates and a teacher at Jonesboro Westside Middle School. The pair opened fire on students and teachers after Golden pulled the fire alarm. Johnson was then 13. Golden was 11.

Johnson was released from federal custody in 2005 when he turned 21. Golden turned 21 this year and was presumably released from federal custody, although authorities have not confirmed that, citing privacy laws.

Johnson was released on $5,000 bond and a trial date was set for Dec. 3. He faces a maximum penalty of 10 years in prison and a $250,000 fine if convicted, Groom said.