Philadelphia police say Smith, who was 16 years old when he was arrested, killed 16-year-old Luis Navarro III for Navarro's dirt bike.
We're told an alert citizen tipped off police when he saw a group of young people moving the stolen bike from one house to another.
Investigators told Action News that on July 28, 2007, Smith was waiting on a bike path for Navarro. When Navarro approached, the Smith jumped out into the path and pulled out a gun, according to police, and demanded that Navarro get off his new dirt bike.
Police say when Navarro swatted away the gun and started to drive off, Smith fired the gun and the bullets hit Navarro in the back, killing him.
Navarro's parents gave him the $3,000 dirt bike a week earlier for his birthday. Family members said teen was so thrilled that he slept next to it for five days in the basement, where it was parked between his bed and a shelf brimming with Spider-Man figurines.
Smith's sentencing is slated for October 24, 2008.
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