A man was found guilty of first-degree murder on Friday for fatally shooting a 12-year-old boy at the Alemany public housing complex in San Francisco in 2002, prosecutors said.

William McKnight, 37, shot and killed Keith Frazier, on May 17, 2002, in the 900 block of Ellsworth Street in the city's Bernal Heights neighborhood.

McKnight was apparently targeting Frazier's older brother, Kevin Wortham, who he believed was responsible for a murder earlier that year, police said.

Wortham was giving Frazier and their 3-year-old sister a ride home when the shooting happened. Frazier was hit several times by the gunfire, while Wortham was grazed by a bullet, prosecutors said. The young girl was uninjured.

McKnight fled after the shooting and eluded authorities until 2010, when he was found in Texas and extradited back to San Francisco.

A San Francisco Superior Court jury deliberated for nearly four days before finding McKnight guilty of one count of first-degree murder and one count of attempted murder with gun enhancements, prosecutors said.

"This defendant murdered a 12-year-old boy in front of his little sister, and thought he could make a run for it," District Attorney George Gascon said in a statement.

"The victim's family may never be the same, but thanks to witnesses who came forward, justice was served," Gascon said.

McKnight faces a possible sentence of up to 79 years to life in prison, and was due back in court today for post-trial motions.