I remember seeing him in a play at the Mark Taper Center that my mother took me to when I was younger. It's not listed in his Broadway Database. We may remember him as Big Kathy in A Rage in Harlem, but he was so much more.
A Los Angeles Times Obituary
What Would Thembi Do discusses his obscure status in film contrasting his roles in plays. She also reminds us how close the apartheid era still is and Mokae's period in exile from South Africa.
I looked for an LA Sentinel article but they'll probably print it two weeks after his funeral.