Officials say the weapon was recovered from a high-ranking gang member on Long Island.
Suffolk County District Attorney Thomas Spota says Alvaro Delgado indicated the gun "has 10 bodies on it."
Spota says Delgado is a high-ranking member of the El Salvador-connected MS-13 gang. Some of the six suspects in last year's Newark schoolyard slayings were thought to have ties to the gang. Essex County authorities downplayed those allegations.
The gun was seized March 24 as part of an ongoing weapons crackdown on Long Island.
The victims in the Newark slayings were shot in the head after being ordered to kneel in front of a wall. A fourth friend survived.
Dashon Harvey, 20, Terrance Aeriel, 18, and Iofemi Hightower, 20, were shot execution-style behind an elementary school. Aeriel's 19-year-old sister, Natasha - who also attends DSU - also was wounded in the Aug. 4 shootings, but she survived.
