The impassioned held signs and called out the names of George Floyd and Breonna Taylor.
The group started out smaller outside the Hall of Justice then grew to a massive size as the demonstration moved toward the steps of City Hall.
One protester, who wanted to be identified as Jane Doe, held a sign stating, "This is 4 my great-great-grandma. Black Lives Matter."
She said she decided to participate in the protest to represent her great-great grandmother and her family.
"I'm here fighting for her today because my family is from the South, and I wouldn't be here without them, and we still are facing many inequalities today. This is for my great-great-grandma and my ancestors before that because we're still fighting for equality just like they were in the 1900s. This is for them. I wouldn't be here if it wasn't for them," she said.
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She said she felt compelled to participate in demonstrations and could not just sit back and watch.
"I had to be out here protesting because the inequality is not OK. I see it everyday. I faced it myself. It's not OK, it's not," she said.
She said Wednesday's protest was the first one she's ever joined, describing the energy at the events as positive and peaceful.
"It's just wild. You see every single race out here fighting for us," she said. "It's more love than hate...There's no rioting. I don't expect any violence today...I have to stand up for what I believe in, and this is it."
Black Lives Matter activists have been protesting against Lacey every week at her office at the Hall of Justice. The group was expected to march there from City Hall later in the day. The activists have criticized her for failing to prosecute police officers accused of misconduct.
Lacey joined Eyewitness News via Skype to respond to the protest outside her office. She said she supports the demonstrators' rights to protest but wanted to provide her side of the story.
"I just want to let people know it's not accurate. The L.A. County District Attorney's Office under my leadership has actually prosecuted more than 20 officers for use of force," she said. "My record on this issue is greater than anybody who's promising that they're gonna bring them more."
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"These are heartbreaking times, and I just want to state unequivocally once again that I too am angry over the way that George Floyd was murdered. I'm grateful that all the officers were arrested today," she added.
Lacey said she wants to have a dialogue with the protesters, though likely not in the middle of the actual demonstration.
"If you could imagine, if I went out there to talk to a mob of people right now, there'd be no chance for dialogue, and all I'm asking for is dialogue," she added.
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