Rodney King was found dead in the swimming pool at his home in Rialto, Calif., on Sunday, police said. He was 47.
King's beating by police in 1991 was caught on videotape and then sparked riots in Los Angeles when police accused of excessive force were acquitted.
Capt. Randy DeAnda told CNN that the Rialto Police Department received a 911 call from King's fiance early Sunday morning. Police responded and found King unconscious at the bottom of the pool. He was transported to the Arrowhead Regional Medical Center, where he was pronounced dead.
DeAnda said there were no signs of foul play and that police were conducting a drowning investigation.
"Rodney King was a symbol of civil rights and he represented the anti-police brutality and anti-racial profiling movement of our time," the Rev. Al Sharpton said in a statement. "It was his beating that made America focus on the presence of profiling and police misconduct."
In an April interview with NPR's Karen Grigsby Gates about his new book, King, who had struggled with alcohol, seemed contented, sober and engaged. He said he had come to grips with the night in 1991 when he was stopped by police and beaten, kicked and tasered.
King was drunk when he was pulled over by Los Angeles police for speeding. A civilian bystander videotaped as the officers proceeded to repeatedly beat him. Four of the officers were charged with excessive force, but a year later, a mostly white jury acquitted them.
Their acquittal triggered the worst riot in modern U.S. history. After five days, 53 people were dead and thousands were injured. More than a billion dollars in damage was estimated.
King eventually received almost $4 million from the City of Los Angeles in a civil suit. He was engaged to Cynthia Kelley, a former juror from that trial.
He published a book this year, The Riot Within, about how that night affected him.
Update at 3:32 p.m. ET: NPR's Allison Keyes Remembers King:
Reporting for weekends on All Things Considered, Allison spoke to LA-based civil rights leader Connie Rice who saw King at a recent forum.
"Three weeks ago when I saw him, he'd never looked better," she said. "He looked healthy. He didn't look haunted anymore."
Allison reports that King and those who knew him acknowledged his battle with alcohol.
"He recently said his sobriety was a work in progress," Allison said. "He had several run-ins with the law after the beating. But King's issues didn't detract from the awe he inspired in many communities."
The Rev. Jesse Jackson Sr., the civil rights leader, says the filmed attack on King made it impossible for people to dismiss similar incidents.
"It served to illuminate the darkness on the issue of race profiling and police brutality," he said.
Update at 2:46 p.m. ET: NPR's Karen Grigsby Bates Remembers King:
In an interview on Weekend Edition Sunday, NPR's Karen Grigsby Bates said she was surprised to hear King was found unconscious in his pool. Bates interviewed King when his book came out last April. At the time, he told her "water was his therapy."
"[He said that] when he had a bad day he liked to get into the pool or — if he could get to the beach — take his surfboard out and surf," she told host Rachel Martin.
She said police do not suspect foul play and think his death was accidental.
In April, King told Bates he was looking forward to "the second half of his life." She described him as open, warm and confident — a contrast to the scared man who asked "Can we all get along?" 20 years ago as rioters raged in Los Angeles.
Listen to Bates talk about King on Weekend Edition by clicking the audio link below: