The handgun is a 9mm pistol, said Chambersburg Police Chief Michael DeFrank. The weapon has been sent to the Pennsylvania State Police crime laboratory in Harrisburg for testing.
Several witnesses to the 5:31 p.m. shooting also identified Jefferson as the person who shot Green, court records said.
No prior criminal record is on file under Jefferson's name in the office of District Attorney John F. Cherry in Harrisburg.
Green was one of two victims in a drive-by shooting on July 20 on West South Street. In that incident, he was wounded in the chest and the left wrist by bullets fired from a vehicle into a group of people standing across from the Laurel Lodge facility. He was treated at Chambersburg Hospital.
Chambersburg Police found Green lying face-up on the sidewalk Monday just steps from his home. He had a single gunshot wound to the chest and had no signs of life when police arrived, court documents said.
Police released no details of the shooting on Tuesday. On Monday, DeFrank said it was not a drive-by shooting.
Police have not determined whether the shooting was gang- or drug-related, DeFrank said.
A preliminary hearing for Jefferson has been set for 1 p.m. Oct. 16 before District Justice Gary Carter.
Damon L. Bryant, 20, of 40 S. Main St., also was injured in the July drive-by attack when he was shot in his left leg, shattering the femur. He was treated at York Hospital in York, Pa.
Three Chambersburg teens and a 24-year-old have been charged in connection with the drive-by shooting.