There has been no lack of similar cases in the last few years, and in 2016 alone, at least 115 black men have been gunned down by on-duty officers. As a result, activists have been keen on keeping victims' names in the public consciousness.
But not since the 2014 police-involved deaths of Michael Brown in Ferguson, Missouri, and Eric Garner in New York City, has the civil rights activist community been galvanized to speak so resoundingly of its heartbreak and outrage over a string of cases. And, as in 2014, the response has shown generational differences in strategy.
Prominent voices in the Black Lives Matter movement lean on social media to publicize injustice and mobilize protesters, while legacy organizations tend to seek out cameras and issue statements via press release. That's been the case in the reaction to Sterling, who died Tuesday after a confrontation with police outside of a Baton Rouge, Louisiana convenience store. And to Castile, who died Wednesday after a patrolman stopped him and his girlfriend near St. Paul, Minnesota.
While the social media-driven Black Lives Matter movement has been viewed as the millennial generation's version of legacy organization's marches and sit-ins, both approaches mirror a diverse tradition of black activism in the U.S.
"I think we can say that it's all necessary and, unfortunately, it's very necessary," said Rob Widell, an associate professor of history at the University of Rhode Island in Kingston whose work focuses on of the civil rights movement, in a phone interview on Thursday. Because violence against African-Americans is an "age-old thing," he noted, the activist response has always pointed toward a call for justice and police accountability.
More established civil rights leaders in the late 1960s and 1970s took measured steps if meet with city council members and mayors on policy matters, Widell said. But in places like Birmingham, Alabama, groups such as the Alabama Black Liberation Front employed more in-your-face tactics that circulated mimeographed images of police brutality victims in and outside of the black community. Both strategies led to unseen gains in political power, according to Widell.
Last summer, leaders of the NAACP, the nation's oldest and largest civil rights organization, marched 1,002 miles from Selma, Alabama — the site of historic voting rights actions — to Washington, D.C. to demand Congress pass policing reform legislation, the Law Enforcement Trust and Integrity Act and the End Racial Profiling Act.
That march happened as activists in the Black Lives Matter movement came together last August for an unprecedented convening. Organizers said they wanted to reclaim the legacy of civil rights icons like Martin Luther King, Jr. Attendees also offered therapy-like sessions for activists who had endured violent crackdowns on protests and other supportive services to continue their local work.
The result of Black Lives Matter efforts and traditional civil rights advocacy was a political environment in which largely Democratic politicians were forced to take position on policing reform matters. During the Democratic presidential primary, candidates also felt some pressure from activists to state, unequivocally, that black lives matter.
"One of the things that we can say pretty absolutely is that any successful effort to bring about change is going to require action on multiple fronts," Widell said.
Here is a sampling of how activists across generations are responding to the recent events:
Voices of the Black Lives Matter movement
Prominent voices of the movement, such as DeRay Mckesson, Johnetta Elzie and Jessie Williams, took to Twitter to voice the grief and exhaustion felt throughout the black community.
The National Action Network
The Rev. Shelton Charles Dixon, a local NAN branch leader in Sterling's hometown, Baton Rouge, Louisiana, wrote a letter to NAN founder Sharpton, which was shared online, in which he requested Sharpton's presence.
There will always be emotion evoked in the immediate aftermath of a tragedy like this and when there is a life lost. We are seeking the involvement of an organization like National Action Network because we want to ensure that the fight for justice will continue even when the cameras go away.
Rev. Jesse Jackson and the Rainbow PUSH Coalition
Jackson, the civil rights icon who worked alongside the Rev. Martin Luther King, Jr., praised local authorities for allowing the U.S. Department of Justice to conduct a federal probe related to Sterling's death. His statement was emailed to Mic on Wednesday.
The two police officers who shot and killed Alton Sterling while he was face down in a convenience store parking lot in Baton Rouge, La., should be arrested and charged immediately. It was a public execution, a legal lynching. They should not be on leave. They should not be placed on desk duty, collecting a paycheck, while children weep... The community is aroused. This is more Trayvon Martin. This is more Eric Garner and Michael Brown. The politics of our time has made this all the more possible. This is the toxic environment that we are now breathing. It is time to clear the air with the disinfectant called justice.
Cornell Williams Brooks and the NAACP
Brooks released a statement online Wednesday calling on state leaders in Louisiana to allow federal intervention in Sterling's death and help foster trust between the community and law enforcement.
Beyond heartbreaking, this latest tragedy calls for officials to break the inertia that may paralyze local and state authorities in insuring justice for the family, friends and community of Alton Sterling.
Marc Morial and the National Urban League
The NUL president and Louisiana native urged state authorities to take heed of what the federal infestation reveals in the probe of Sterling's death. His statement was emailed to Mic on Wednesday.
Louisiana has had its fair share of national tragedies and continues to march toward the north star of equality. 'Union, Justice, and Confidence' is the state motto and those words are to be made ever more significant in the coming weeks as investigations reveal more.
Although many of the statements released by activists and organization on Tuesday and Wednesday were reactions to the Sterling case, leaders individually reiterated their calls for justice after the news of Castile's death.
July 8, 2016, 2:46 p.m.: This story has been updated.