"If we can't figure out who killed Biggie, or who killed Tupac, or who killed Jam Master Jay? Or any of the famous rappers who've been murdered. How many murders do you think we're solving in these communities?" Simmons said on Wednesday morning.
"People are murdering each other without any recourse," he said during the press conference. "We need to get in our communities and work from the inside out, but we cannot do it alone. We need support."
The rally, part of Peace Week, was organized by Erica Ford, who is a long-time leader against violence in the city.
"Today, we come together as anti-violence leaders, young people, elected officials, celebrities and family members of those impacted by youth violence to join forces to change the culture of violence," Ford said. "Peace can be a lifestyle."
Ford picked up additional support from Brooklyn rapper Maino, who has turned his life around after serving 10 years in prison for kidnapping.
"I, personally, come from the same community, and the same violence," the "Hustle Hard" rapper said.
"I know what it is to be a part of gun violence, to lose friends, to lose families. However, this is the flip side to it," he said, referring to mothers at the rally who lost sons to gun violence.
"We read about this violence. We read about these kids that's getting murdered. But we never meet the families, and the loved ones," he said. "I'm just here to play whatever part that I need to play."