Bob Moses, the iconic Civil Rights leader who relentlessly fought to register black voters in Mississippi in the 1960s, passed away on Sunday in his Florida home, the New York Times reports. He was 86 years old.

Raised in the Harlem River Houses housing complex, Moses attended Stuyvesant High School, a competitive school that focused heavily on math. He then went on to play basketball and major in philosophy and French at Hamilton College in Clinton, N.Y, and earned a philosophy master’s degree in 1957 from Harvard University.

In 1960, Moses taught math at the private Horace Mann School in Bronx’s Riverdale neighborhood when the south’s civil rights movement emboldened him to travel to Mississippi. Once there, he helped poor, illiterate Black residents register to vote and get an education in makeshift freedom schools. His efforts drew violence and resistance from white segregationists and local law enforcement.

Per NYT, he was arrested and jailed dozens of times and was once shot at by three Klansmen and beaten by a sheriff’s cousin during a voter registration drive. He developed a reputation for being able to remain tranquil and calm in the face of brutal violence.

Among other accomplishments, Moses started the 1984 Mississippi Freedom Summer Project, which recruited college students to aid in voter registration campaigns around the state. His work as an activist was so prolific, that Moses became the subject of 2000’s Freedom Song, which starred Donald Glover. He often credited his parents for his love of learning and education and recalled in an interview that they would collect books for him from a Harlem library and encourage him to read and be educated.

Moses is survived by his wife, his two daughters, his two sons, and his seven grandchildren.