"The only way you see change, you have to become change," Mourning said.
Rev. Al Sharpton vowed on Sunday to continue rallying on behalf of Trayvon Martin until the teen's shooter was arrested.
Sharpton, Jesse Jackson, singer Chaka Khan, Alonzo Mourning and others were joined by the teen's parents, Sybrina Fulton and Tracy Martin, at a rally for him in downtown Miami where several thousand attended.
Martin, a Miami Gardens teen was shot by neighborhood watch volunteer George Zimmerman in February. He had been visiting with his father at his father's girlfriend's home in a gated Sanford community and had gone to buy a bag of Skittles and iced tea at a nearby convenience store. He was walking back when the shooting happened.
"I promised them that we would be here until Zimmerman is arrested," Sharpton said of the teen's parents.
Though Martin was unarmed, Zimmerman told police the shooting was self-defense, and no charges have been filed in the case. Police did not initially charge Zimmerman because of a state law allowing someone to use deadly force if his life is in danger.
Zimmerman's brother said the neighborhood watch volunteer was in a fight for his life the night of the shooting, and insists the cries for help heard on a 911 call from the scene are his brother's.
But MSNBC reported that according to two forensic voice identification experts, the voice on the recording was not George Zimmerman.
"The tests concluded that it's not the voice of Mr. Zimmerman," MSNBC quoted Tom Owen, of Owen Forensic Services LLC, as saying.
"I didn't come to try Zimmerman. I came to say, 'What is good for one, is good for all. Zimmerman, tell it to the judge," Sharpton said. "You had a 9 mm. He had some Skittles. What were you defending yourself from?"
Jackson asked the supporters to not give up.
"Stay in it for the long haul. Keep hope alive," Jackson said. "In the real sense, the question becomes how we turn our pain into power, how to turn a crucifixion into a resurrection, how we go from a moment to a movement."
He also said the Stand Your Ground Law must be repealed.
"Stand tall, don't give up. Wear your hoodie. On your hoodie, wear your voting card. If there's no voting card on your hoodie, you are being hoodwinked," Jackson said.
Meanwhile, Sybrina Martin told the supporters about her grief.
'We've been to a lot of places, but this means the most to us," she said. "A lot of people ask me how do I stand up and my child is shot and killed. It is God that is holding me up. I believe justice will be served," she said.
Florida Gov. Rick Scott has appointed a special prosecutor to oversee the investigation into the death. The FBI and U.S. Justice Department are also investigating the shooting.
"There are strength in numbers," Mourning said. "The only way you see change, you have to become change."
Miami Commissioner Michelle Spence-Jones told the crowd: " We will stand our ground."
"Miami, make no mistake, this is our wake up call," Spence-Jones said. "Today I challenge you to stand up to do something ... We need to make sure that Trayvon does not become another statistic."
"Today I simply tell you this: I show up, I stand up and I speak up for Trayvon. I show up, I stand up and I speak up for my son," said Miami-Dade Schools Superintendent Alberto M. Carvalho.
Before the rally, Congresswoman Frederica Wilson, who organized the event, said she wants an immediate arrest in the case. She added that she feels the Sanford Police and the local prosecutor there have not done their jobs.
Martin's aunt, Angela Owens, said the teen was a mild-manned child, not a troublemaker. She said the family was shocked by what happened and they want justice.
Grammy Award winning R&B artist Betty Wright sang her song "Dry Well." It is the song she wrote to honor her own child who was killed.
"Trayvon shook us and woke us up," she said. "We were sleeping," Wright said.
Wright exclusively told NBC 6 that her 21-year-old son Patrick Parker was fatally shot on Christmas in 2005 and like Martin's, his killer was never arrested.
"There is a solidarity that hasn't been seen in many years and this one young man, little hoodied boy, with his Skittles and iced tea, has rocked the world," Wright said.
Communities all across the nation that have been galvanized by the event. The shooting has led to numerous marches and protests throughout South Florida and across the country, as Martin's family and supporters demand Zimmerman's arrest.
More than 2.2 million people have signed the Martin family's online petition demanding Zimmerman's arrest and prosecution.
Sharpton is the host of "Politics Nation" on MSNBC, which is also owned by NBCUniversal.
He also gave $1,000 to the family and asked others in attendance to do the same.