According to CNN:

Brown died early Monday at Atlanta's Emory Crawford Long Hospital of
congestive heart failure, his agent said. He was 73.

Brown was in Atlanta for a dental appointment when he fell ill and was
admitted to the hospital over the weekend for treatment of "severe
pneumonia," said his agent, Frank Copsidas.

"It appears what happened is that he did die of a heart attack as a
result of his pneumonia," Copsidas told CNN Radio.

Mike