Across the country on Tuesday, community members, activists, racial justice advocates, and others held a global moment of silence to mark two years since the killing of Mike Brown Jr., whose death at the hands of a Ferguson, Missouri police officer sparked a national call for change—a moment that many say has yet to arrive.

"On Saturday, August 9, 2014, the entire world was impacted by the murder of Michael Brown Jr.," wrote the Chosen for Change foundation, created in his honor. The group asked supporters to be silent for four and a half minutes, beginning at 11:55am CDT, to represent the four and a half hours Brown "laid on the hot street in the middle of Canfield Green Apartments in ‪Ferguson, Missouri."

Brown, a black 18-year-old, was unarmed when he was shot by white officer Darren Wilson. His brutal and unnecessary death prompted fierce community protests and national outrage from a community that had long been the victim of systemic discrimination and abuse by the U.S. criminal justice system.

"Hands Up, Don't Shoot" and "Black Lives Matter" became the national rallying cry to address those grievances, and the movement swiftly followed.

As people shared their mourning and reflections on social media, many expressed how Brown himself "doesn't know it but ... changed all of our lives & sparked a revolutionary fire that will never be extinguished," as activist Delo Taylor put it.

Similarly, columnist Kristen West Savali wrote at The Root on Tuesday:

There have been many apt comparisons made between the Watts rebellion of 1965 and the Ferguson uprising, which happened almost 50 years later to the day. Still, the small Missouri town became this generation’s Selma, Ala., a sacred place, a mecca to which social-justice warriors felt compelled to trek. Michael Brown became our Jimmie Lee Jackson, Darren Wilson became James Bonard Fowler and we became filled with the "fierce urgency of now." My feelings this time last year were clear: "The anger—hot, hard, fast—intensified until the words '[F–k] the police' burst free. That guttural call-to-arms, which has seared the Hip-Hop generation’s consciousness since N.W.A. put our collective frustration into words, found a home amid the cacophony of rage building on social media and the streets of Ferguson where a community unchained refused to be silenced, even as police tanks and dogs tried their best to intimidate them." Those feelings remain firmly intact.

New York Daily News columnist Shaun King shared on Twitter his thoughts on Brown's "deeply unjust" killing, adding: "I do believe that #MikeBrown is a martyr. His death, and the injustice surrounding it, sparked the movement we are in right now."

In a series of tweets, activist and St. Louis native Brittany Packnett, recalled how she had "never seen such courage" as she did in the Ferguson protesters while organizer DeRay McKesson compiled a visual history of how the movement unfolded in the wake of Brown's killing.

#MikeBrown and the young people of #Ferguson forever changed my life. They changed the world. They changed all of us. — Brittany Packnett☔️@MsPackyetti) August 9, 2016

"We're still fighting for you," the Black Youth Project promised. "Rest powerfully."

Indeed, others—including Erica Garner, whose father Eric was also killed by New York City police—noted how the fight for racial justice has yet to provide substantial change.

2 years later ... still no justice... SHUT IT DOWN! #mikebrown — officialERICA GARNER (@es_snipes) August 9, 2016

On Tuesday, mourners left bears with the names of other black victims of police brutality at the site where Brown was killed.