FILE - A woman with "Black Lives Matter" written across her cheek attends an ATlanta demonstration against the deaths of unarmed black men at the hands of white police officers.
FILE - A woman with "Black Lives Matter" written across her cheek attends an ATlanta demonstration against the deaths of unarmed black men at the hands of white police officers.

WASHINGTON - Twenty-four years ago today, when four white police officers in Los Angeles were acquitted of brutally beating a black man even though their actions were caught on videotape, the California city erupted in riots so severe they drew comparisons to 1960s civil rights unrest.

Rodney King had been caught by police after a high-speed car chase a year earlier, and an amateur cameraman filmed as the officers pulled him from his vehicle and kicked, beat and clubbed him for more than a minute. The tape was released to news outlets and the event became infamous as a symbol of U.S. police brutality.

King's plaintive comment to the media during the riots  "Can't we all just get along?" became shorthand for the negative impression of U.S. race relations that emerged from the riots.

The Los Angeles riots that broke out that April 29 lasted nearly a week and killed 55 people before peace was restored. King's assailants were later convicted on federal charges of violating his civil rights.

While the events of 1992 at the time seemed to echo the past, the underlying tensions involving race and justice – never fully addressed – still reverberate today.

The current wave of racially charged incidents began on the opposite side of the country in Florida. On February 26, 2012, Trayvon Martin, an African-American teenager, was shot to death by George Zimmerman, a white neighborhood watch volunteer in Miami Gardens. Initially, Zimmerman was not charged in the death because of a Florida self-defense law, but a public outcry led to later charges of manslaughter and second-degree murder. Zimmerman was acquitted. The ruling in 2013 stirred up a new round of unrest.

FILE - Demonstrators block traffic on a highway in
FILE - Demonstrators block traffic on a highway in Los Angeles as they protest the acquittal of George Zimmerman in the Trayvon Martin trial on July 14.

Hashtag becomes social movement

Expressing the dismay that many blacks and whites felt over the seeming imbalance in the U.S. justice system, activist Alicia Garza reacted in a Facebook post, saying "Black people. I love you. I love us. Our lives matter. Black lives matter."

A fellow activist created a Twitter hashtag quoting Garza: #BlackLivesMatter. A 21st-century civil rights movement suddenly had a name.

Meanwhile, incidents of police violence against minorities started getting noticed, with each new incident thrust into the spotlight because of its similarity to the last.

In July 2014, New York City police wrestled 43-year-old Eric Garner to the ground, attempting to arrest him for selling cigarettes illegally. In a video taken by a bystander, Garner, held in a chokehold by one of the officers, is heard to say repeatedly, "I can't breathe," before losing consciousness.  A grand jury decided not to indict the officer for the death. "I can't breathe" became a rallying cry.

One month later in Ferguson, Missouri, a white police officer shot to death 18-year-old Michael Brown, who was African American and unarmed. When a grand jury failed to indict the officer, protests erupted nationwide.

In April 2015, Baltimore, Maryland, police arrested Freddie Gray, a 25-year-old African American. Gray died a week later of injuries sustained during the arrest. As news of his death surfaced, riots broke out in Baltimore. The city was put under a state of emergency order that lasted nearly three weeks.

The extraordinary attention paid to those events and many more like them between 2012 and today have given rise to several iterations of the Black Lives Matter movement. One faction, founded by Garza and her fellow activists, says it remains diffuse and grassroots-focused; other activists have appropriated the name to form political action committees, or PACs.

FILE - Officers and protesters face off along West
FILE - Officers and protesters face off along West Florissant Avenue in Ferguson, Mo., Aug. 10, 2015.

Grassroots action, political action

A St. Louis, Missouri-based PAC called Black Lives Matter focuses on voter education in races for law enforcement positions, while the New York-based Black Lives Matter Super PAC hopes to generate large donations from celebrities to contribute to selected political candidates.

Local chapters of groups calling themselves Black Lives Matter have effected change in Boston, Massachusetts, where they protested the city's bid to host the Olympic Games because they said it would be harmful to black neighborhoods. (Boston ended up withdrawing its bid.) Other groups in other cities conduct nonviolent protest workshops, protest other police shootings, and organize diversity-focused public events.

As the U.S. presidential and congressional elections draw near, what remains to be seen is how much influence groups under the Black Lives Matter umbrella can impose on the selection and direction of the national government.

Black Lives Matter activists have met with Democratic presidential candidates Hillary Clinton and Bernie Sanders to discuss their positions on race and the justice system.

Campaign Zero, a Black Lives Matter offshoot that focuses on police violence, promotes policies such as ending "stop-and-frisk" racial profiling and establishing civilian oversight structures to weigh in on police department policies.

Last October, both the Democratic and Republican national committees responded to a Black Lives Matter request for a presidential debate on BLM issues. The committees have said they would not alter their debate schedules, but would support a town hall format.

With the election still months away, it remains to be seen exactly how and how much the movement will affect the outcome of the presidential contest. But the actions of the movement thus far give its supporters some hope: that 20 years from now, things will be different.