PHILADELPHIA — A teenager was shot in the back just minutes after his high school graduation at a Temple University sports arena.

Khiry Caldwell, an 18-year-old graduate of Strawberry Mansion High School, was shot at 4:15 p.m. Tuesday outside the Liacouras Center in North Philadelphia.

Caldwell suffered a broken rib and a bruised lung but was in stable condition at Temple University Hospital.

Later, he was alert, laughed with family members and friends at the hospital and joked about wanting a cheesesteak, his father, Amin Caldwell, told the Philadelphia Daily News. He said doctors would not allow the teenager to sit up because of his back injury.

Authorities said two groups of five or six young men started fighting soon after students emerged onto Broad Street carrying their diplomas and taking photos.

Two shots were fired, both hitting Caldwell, police said. Temple police drove him to the hospital.

Caldwell's parents, Amin and Kathy Caldwell, said their son was a bystander.

Police were trying to determine if the teens in the fight were also graduates. Authorities said there has been an ongoing battle between two groups at the school. Sgt. Ray Evers said the bullets came from a .22-caliber handgun, which had not been recovered.

Amin Caldwell said his son kept out of trouble and worked as an attendant at a neighborhood gas station. School district spokesman Fernando Galliard said the high school's principal described Caldwell as a very good student who has plans to go to college.