A geeky Harlem 13-year-old named Elmo coldly opened fire on a teen rival to avenge a humiliating beatdown, sources said yesterday.
Cops nabbed nerdy Elmo Williams after he allegedly tried to shoot a 14-year-old tough at about 3 p.m. Thursday in front of the Jefferson Houses in East Harlem.
Sources said Elmo — described by shocked neighbors as an avid computer gamer not known for violence — had recently been jumped by the older boy, said to be a member of a crew called 10-40.
“They were two rival gangs,” a source told The Post. “The two kids had previously gotten into a fight, so yesterday Elmo decided to shoot at the kid from across the street.”
No one was struck, and Elmo dropped the gun and bolted when cops intervened. He was collared almost immediately.
Elmo claimed he “just found” the weapon, a source said.
The Interarms Star 9mm handgun — which sells for about $275 online — is known as a bargain-basement gun.
Elmo’s Hamilton Heights neighbors described him as more of a geek than a gunman.
“I would put my hand in the fire for him,” said Melquy Berndez, 49. “Not him. I can’t understand it.”
He said Elmo lives with two brothers in a strict household where his dad, reportedly a city worker, and mom don’t permit riffraff.
A 13-year-old boy named Matthew said Elmo is just an introverted kid who plays it straight.
“I’m shocked,” Matthew said. “It’s not something I expect him to do.”
The gunfire in broad daylight spooked neighbors.
“It was ‘Boom!’ That’s it,” said Yen Zhou, 40, who was at the register at El Barrio Wine Liquor across East 115th Street from the shots.
“Some kids were running across the street, and then the cops came. A lot of cops.”
Detectives pored over security video from Solestice shoe store, where a worker, who declined to give a name, told The Post there were “just two kids kind of jogging past in a hurry.”
Elmo was set to cool his heels at a juvenile-detention facility after he was brought before a judge in Family Court in lower Manhattan, a city Law Department spokeswoman said.
He’s due back Feb. 11, when city lawyers plan to formally charge the youth.
Additional reporting by Georgett Roberts, Laura Italiano and Aaron Feis