Police say a teenager used a 9mm semi-automatic rifle in firing shots at a northern Illinois high school before he was stopped by a school resource officer.
Illinois State Police said Thursday that 19-year-old Matthew Milby's mother bought the weapon in 2012 and that investigators were working to determine how he obtained it.
Milby is being held on a $2 million bond for aggravated discharge of a firearm charges in the Wednesday morning shooting at Dixon High School. Police say he was wounded by the officer and transferred Thursday from a hospital to jail.
No one else was injured at the school about 80 miles (130 kilometers) west of Chicago.
Sauk Valley Media reports Milby was convicted in April of marijuana possession and fined $120.