Police said 18-year-old Zahmir White was last seen in South Philadelphia.
Witnesses identified White, who goes by Pikachu on the streets, as the man who fired a 9MM semi-automatic gun at 16-year-old William Bethel on the 800 block of South Street Easter Sunday.
"They were just bouncing around South Street the way a lot of kids do and they happened upon each other," said Philadelphia Police Capt. John Ryan. "As we understand it, it was an argument. A foolish argument between kids over nothing substantial that led to this."
Ryan said investigators believe it was an argument over a woman.
Police have not said if that woman was a girlfriend or how she became the focal point of the feud. A weapon has not been recovered.
The victim, who many called Bill, lived in Roxborough but was visiting friends in South Philadelphia.
The honor roll student at Boys Latin Charter School died days later from his injuries.
Police said Zahmir White is known to frequent South Philadelphia, Southwest Philadelphia, and Upper Darby.
Anyone with information is asked to contact police.
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