Chicago Mayor Rahm Emanuel, Philadelphia Mayor Michael Nutter and New Orleans Mayor Mitch Landrieu were all there.
"It's not just about race, not just about guns, it's about a culture of behavior that has been created for a whole bunch of reasons," Landrieu said.
In New Orleans last week, 18-year-old Joseph Massenburg of Matteson was murdered. Massenburg was in New Orleans volunteering with AmeriCorps.
He was talking on his phone when he was gunned down.
Police in New Orleans have no motive and no suspects.
After the shooting, AmeriCorps pulled two of its service teams out of the city.