CINCINNATI, Ohio (CNN) -- Maya Angelou is praying for the family of slain teen Trayvon Martin.
The author and civil rights activist joined Martin's parents in Cincinnati Wednesday for a panel discussion on violence and racial healing.
Neighborhood watch volunteer George Zimmerman is charged with second-degree murder in the Martin's February death in a central Florida subdivision.
Zimmerman says he shot Martin in self-defense during a struggle. The Florida teen was not armed.
Angelou says his family needs to stay strong.
"I told them this morning, I've been on my knees with them, in prayer with them, since the tragedy. And my prayer for them is to be strong. Continue to be strong. And if, in fact, the root is not, if he is exonerated, it's very difficult to go to -- avoid being bitter," Angelou said.
Zimmerman has pleaded not guilty.
He has been free on $1,000,000 bail since earlier this month.