One man fired eight shots into the car, striking the 13-year-old boy in the car's passenger seat.
Witnesses, including the detective, told investigators that the gunman seemed to have targeted the teen.
The victim was hit in the shoulder and leg, and was taken to CHOP, where he was listed in stable condition last night, Small said.
The detective who witnessed the shooting followed the suspected shooter and another male, and saw them walk into a home half a block away on Mountain Street near 20th, where police set up a barricade involving SWAT and Fire Department personnel.
The home's owner came out and was taken into custody, interviewed as a person of interest in the shooting, Small said. It was unclear last night if he was thought to have been involved with the shooting. By the time cops entered the home, the two suspects had apparently fled.
He told police that the two men stormed into his home without warning. After clearing the house, the SWAT officers found two handguns hidden in a golf bag on the first floor, Small said.
The shooting victim and his stepfather, who was driving the vehicle, told investigators that the shooting was fueled by a bike theft Sunday. But the teen was the owner of that stolen bike, Small said.
"We're trying to figure out why someone felt the need to shoot a teenager over a stolen bike," Small said.
Police were searching last night for the two men seen leaving the scene. Witnesses told cops the shooter was a short male between 17 and 21 years old, Small said.
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