He dedicated a song to Trayvon Martin, and then he was attacked on stage.
A video provided by Fuse News shows a woman with long dirty blonde hair shoving soul singer Lester Chambers of Petaluma on stage while he was performing Curtis Mayfield's classic hit "People Get Ready."
Her surprise attack knocked Chambers down on Saturday about 5:15 p.m. at the Hayward Russell City Blues Festival in Hayward, Calif., where a mostly peaceful crowd, many of them wearing tie-dyes, had simply been enjoying the music and hanging out on lawn chairs.
The video shows her giving a hard shove to Chambers and then wrestling with him on the stage and his crew jumped in to stop the fight and pull her off.
The 73-year-old singer was taken to the hospital but has since been released. The video shows him being wheeled off to an ambulance and saying "I'm gonna pray" when a friend asked him how he was.
Police identified the woman as Dinalynn Andrews Potter, 43. Reports and police indicate she yelled "it's all your fault" to Chambers. She was cited and released on suspicion of battery. She is white and Chambers is African American.
Bobbi Goodman of Foster City was there, and also took some video of the concert. She heard Chambers dedicate the song to the slain teen and the aftermath of the attack.
"We were all shocked," Goodman told NBC Bay Area, who added that after 30 minutes, the concert resumed. "They didn't want to let this person ruin everything." As of Tuesday, her video had nearly 43,000 views.
The nation has been on edge since Saturday night, when a jury in Florida found George Zimmerman not guilty of second-degree murder or manslaughter in his fatal shooting of the 17-year-old African-American on Feb. 26, 2012.
Protests have been cropping up around the country, with many upset that Zimmerman was acquitted. Zimmerman has had his share of supporters, too, with many siding with him and Florida's "stand your ground law."