Members of the St. Louis chapters of the NAACP and the National Urban League march on West Florissant Avenue in Ferguson, Mo., on Saturday, Aug. 23, 2014.

ST. LOUIS - Hundreds of people gathered Sunday in St. Louis' largest park for a festival encouraging peace over violence - an event that took on new resonance after the fatal shooting of an unarmed black 18-year-old by a white police officer.

Peace Fest 2014 was already in the works before Michael Brown was killed in the St. Louis suburb of Ferguson. But the shooting and the nightly protests it touched off have put a larger spotlight on the event.

"I think this is divine," said James Clark, vice president of community outreach for Better Family Life Inc., the nonprofit that organizes the festival each year. "The whole world is watching Peace Fest today."

Tracy Martin, the father of slain Florida teen Trayvon Martin, was scheduled to speak at the event at Forest Park, a move that was also set prior to the Aug. 9 shooting of Brown. Organizers said a representative of Brown's family would join Tracy Martin.

Trayvon Martin, 17, was also unarmed when he was shot and killed in 2012. George Zimmerman, a neighborhood watch volunteer who said he shot Martin in self-defense, was acquitted.

The nightly protests in Ferguson have been mostly peaceful in recent days, a contrast to images of police in riot gear firing tear gas canisters at angry protesters in the days after the Brown shooting. Tensions briefly flared then subsided late Saturday night and early Sunday.

Niesha Thomas, who attended Peace Fest, said she hopes the event marks "a new start" in which people put "irrelevant, unproductive" disputes behind them. Musical performances were interspersed with speakers urging people to choose peace over violence.

"This should be a pivotal point where we move forward," Thomas said.

But that might not be so easy. A grand jury has started considering evidence in the case and some local residents and officials have said they're concerned that a failure to return an indictment against Ferguson officer Darren Wilson could stoke new anger in the community.

Missouri Gov. Jay Nixon reiterated his support Sunday for sticking with St. Louis County prosecutor Bob McCulloch. Brown's parents and others in the community have expressed concerns that the office would not be impartial because of McCulloch's ties to law enforcement. McCulloch's father, mother and other relatives worked for St. Louis police, and his father was killed while responding to a call involving a black suspect. He has said he will not remove himself from the case.

"He was elected overwhelmingly by the people a number of times. He's been through a lot," Nixon said on NBC's "Meet the Press." ''Certainly, with this level of attention, I think everyone will work hard to do their best work."

The federal government also has launched its own investigation into the shooting.