The search for the masked gunman who fired a single bullet to the head of Run-DMC star Jam Master Jay has been hampered by silence from the hip-hop world and the streets where he grew up, rap industry notables and police say.

At a news conference promoting a fund for the slain disc jockey's family, musicians and music executives, including rap mogul Russell Simmons, Sean "P. Diddy" Combs, Foxy Brown and Busta Rhymes, pleaded with the public to give money to the fund and phone in tips to police.

The celebrities said they already had contributed tens of thousands of dollars to the fund and would be distributing fliers asking for the public's cooperation.

"A lot of people are silent in the community,'' Simmons said. "The police department is not at fault."

Joe "Run" Simmons also announced that he and Darryl "DMC" McDaniels — the surviving members of the group — would no longer perform as Run-DMC.

Mizell worked the turntables as Simmons and McDaniels rapped a string of hits over nearly 20 years. He had been mentoring younger artists in recent years in the second act of a career that helped make hip-hop commercially viable.