Busta Rhymes said Mr Ramirez was a 'true friend'

Israel Ramirez, 29, was shot outside a warehouse earlier this month where a music video was being filmed.

Commissioner Raymond Kelly said the silence of several potential witnesses was stalling the investigation.

He said of Rhymes: "If your employee's murdered in front of you, you think you might want to talk to the police."

The rapper's publicist declined to comment on the commissioner's remarks.

Unarmed bystander

Rhymes - real name Trevor Simpson - was recording the video for his new song Touch It, when Mr Ramirez was shot on 5 February.

Along with Rhymes, Missy Elliott, Mary J Blige, DMX and members of G-Unit were among 500 people who gathered at the Brooklyn warehouse for filming.

Police say the shooting may have stemmed from an argument that broke out inside and spilled onto the street.

They believe Mr Ramirez, who was unarmed, was a bystander who may have intervened only to protect Rhymes.

The father-of-three died following a single gunshot wound to the chest.

Rare friend

Commissioner Kelly said witnesses could be forced to answer questions before a grand jury if they continue to stall.

He said: "I find it quite disturbing. This individual was shot in front of a lot of people."

Rhymes attended a wake last week at a Manhattan funeral home for Mr Ramirez.

In a written statement, he said Mr Ramirez "was not only security for me, but he was a friend, one of the rare friends that you come across that you can trust with your life".