Exclusive Details

Dave Brockie -- lead singer of the crazy costumed "Beavis & Butthead" worshipped speed metal band Gwar -- is dead at age 50.

Law enforcement sources tell TMZ ... Brockie -- a.k.a. Oderus Urungus -- was found early Sunday morning dead, sitting upright in a chair at his Richmond, VA home.

We're told foul play is not suspected ... and one law enforcement sources told us, "There were no drugs found, as far as I know."

Another law enforcement source tells us it was not a suicide. No note was found. Brockie was found by his roommate.