Rodney King, the African American at the centre of the Los Angeles riots 20 years ago, has been found dead aged 47.
His fiancee found his body at the bottom of a swimming pool, but there was no sign of foul play.
King was a victim of police brutality in 1991, but the officers involved were acquitted the following year.
The verdict triggered clashes between rioters and police which left more than 50 dead and thousands injured.
Rialto Police Captain Randy Deanda said on Sunday King was found "unresponsive" at the bottom of his pool and was pronounced dead at 06:11 (13:11 GMT).
Rodney King's beating at the hands of the police, which left him with brain damage, was filmed by a bystander and shown by media outlets across the world.
He had been stopped for speeding on a dark street on 3 March 1991. The four LA police officers who pulled him over hit him more than 50 times with their batons, kicked him and shot him with stun guns.
A later trial resulted in two of the four officers being jailed. King sued the City of Los Angeles and won $3.8m (£2.5m) compensation.
The rioting that gripped LA in the wake of the original not-guilty verdict went on for days, leaving 50 people dead and causing $1bn of damage to the city.
King went on television three days into the rioting to call for calm, pleading that everyone "just get along".
The Los Angeles Police Department was forced to change in the wake of the Rodney King case, which highlighted widespread racism in the largely white, male force.
It was not uncommon for officers to describe African-Americans as "monkeys" and "gorillas", and some police bragged about beating suspects over their patrol car radios.
An independent commission was set up to investigate the issue, chaired by future US Secretary of State Warren Christopher.
It recommended boosting multiculturalism in the police force and the LAPD had slowly shifted to a more community-focused style of policing.
As for Rodney King himself, he got encaged to one of the jurors from his trial and published a book in 2012 titled "The Riot Within: My Journey From Rebellion to Redemption".
In it, he speaks about his lifelong struggle with alcohol abuse, which has led to him being charged with driving under the influence of alcohol on several occasions.