Isaac Hayes at 21st Annual SXSW Film and Music Festival - Stax Records 50th, Anniversary held at Antone's, Austin, Texas - 15.03.07

Family members found the Walk On By singer slumped by a treadmill at his home gym in Memphis, Tennessee on Sunday (10Aug08); he reportedly collapsed while working out.

And now paperwork filed by Dr. David Kraus suggests the star suffered a stroke, but a full autopsy has yet to be performed.

Source: WENN