FORT LAUDERDALE, Fla. (AP) —  Dr. Robert B. Hayling, a dentist and influential civil rights activist in Florida during the 1960s, has died.

Hayling died Sunday at home in Fort Lauderdale, his sister, Yvonne Hayling-Clarke, told The Associated Press. 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.

They were released only after protests by Martin Luther King Jr., Jackie Robinson and others popularized their predicament, according to the ACCORD Civil Rights Museum.

“He motivated us. He made us feel like we were doing something right, and he backed us up a hundred percent in that,” Audrey Nell Edwards, one of the St. Augustine Four, said in a museum news release.

Hayling also got the attention of Vice President Lyndon Johnson in 1963. Hayling protested St. Augustine’s plan to celebrate its 400th anniversary and status as the oldest city in the U.S. with an all-white event.

Hayling’s objection opened the event, and resulted in two tables being set aside for black people, according to the museum.

“Robert was a wonderful person because he loved to give,” Hayling-Clarke said from her home in Sarasota. “He was always giving someone something, looking out and doing the best for everybody.”

Still, Hayling’s deeds also stoked anger in the community. He was beaten at a Ku Klux Klan rally in 1963, and his home was shot in 1964, killing his dog.

The events in St. Augustine are cited alongside other influential moments in the civil rights movement as key moments that led to the passage of the Civil Rights Act of 1964.

Today Hayling’s house is a stop on the Freedom Trail civil rights tour of important historical landmarks in the city, along with his old dental office, which today is a civil rights museum.

A public service is being arranged in St. Augustine in January, Hayling-Clarke said.