Responding to the the acquittal of George Zimmerman, who fatally shot 17-year-old Trayvon Martin a year earlier, on July 13, 2013, Garza wrote: "We don't deserve to be killed with impunity. We need to love ourselves and fight for a world where black lives matter. Black people, I love you. I love us. We matter. Our lives matter."

Patrisse Cullors responded to Garza's post with the hashtag #BlackLivesMatter.

That hashtag began to circulate on social media, and the pair teamed up with activist Ayo Tometi to built a network fighting for racial justice.

Although the phrase was coined in 2013, it was not until after the August 2014 shooting of 18-year-old Michael Brown by police in Ferguson, Missouri, that it became a potent rallying cry against the police killings of unarmed Black people.