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The Glendale, CA Elks Lodge is investigating a shocking incident that went down in the club a week ago Monday, when a performer sang a song celebrating the death of Michael Brown ... for an audience that included a number of retired and current cops ... and TMZ has the video.

The song was a parody of "Bad, Bad Leroy Brown." Gary Fishell, the performer and a member of the Lodge, changed the lyrics, which include:

Michael Brown learned a lesson about a messin'

With a badass policeman

And he's bad, bad Michael Brown

Baddest thug in the whole damn town

Badder than old King Kong

Meaner than a junkyard dog

Two men took to fightin'

And Michael punched in through the door

And Michael looked like some old Swiss cheese

His brain was splattered on the floor

And he's dead, dead Michael Brown

Deadest man in the whole damn town

His whole life's long gone

Deader than a roadkill dog

The event was the capper for a charity golf event, thrown by retired LAPD Officer Joe Myers, a 32 year veteran who left the force in 2007. We're told 50-60 people attended the dinner, and about half were cops, most of whom were retired. The others were civilians.

Singer Gary Fishell is a P.I. who once worked as an investigator for the Federal Government. His lawyer tells TMZ, Fishell now realizes the song was "off color and in poor taste." The lawyer adds, "He's a goofball who writes funny songs." We asked why Fishell would sing this in a room full of cops, and the lawyer replied, "He thought the room would get a kick out of it."

Joe Myers tells TMZ, "How can I dictate what he [Fishell] says in a song?" Myers goes on, "This is America. We can say what we want. This is a free America." Myers adds ... he's done this as an annual event for decades and has raised a lot of money for charity.

Someone who was at the event videotaped it because they were offended by the song and upset no one was objecting.

A trustee for the Lodge tells TMZ, the dinner was not an Elks Club event ... it was a golf tournament run by Myers and since he was a member he had a right to hold a dinner there.

The trustee tells TMZ many of the hundreds of members of the Glendale Elks Lodge are upset about the song, saying, "It's deplorable and inappropriate and the Lodge will take disciplinary action against [Fishell] and possibly the people who organized this event."