Updated

Dr. Robert B. Hayling, a dentist and influential civil rights activist in Florida during the 1960s, has died. He was 86.

His sister, Yvonne Hayling-Clarke, told The Associated Press on Thursday that her brother died Sunday at home in Fort Lauderdale. No cause of death has been determined.

A member of a group known as "The St. Augustine Four," Hayling spent six months in a Florida jail and reform school in 1964 after he and three other members of the NAACP Youth Council asked to be served at a Woolworth's lunch counter.

According to the ACCORD Civil Rights Museum, they were released only after protests by Martin Luther King Jr., Jackie Robinson and others.

Hayling-Clarke says a service is being arranged in St. Augustine in January.