Gunmen opened fire on a Mother's Day neighbourhood parade in New Orleans, wounding at least 19, including two children, police said.
FBI spokeswoman Mary Beth Romig called it "street violence" and said federal investigators have no indication that the shooting was an act of terrorism.
The southern city has one of the highest violent crime rates in the U.S. The shootings took place less than three kilometres from the heart of the French Quarter.
Police said many of the victims were grazed, and most of the wounds were not life-threatening.
A news release said the wounded included two 10-year-olds. It also said two people were in surgery.
Police saw three suspects running from the scene. No arrests had been made as of late afternoon.
As many as 400 people joined what is known as a second-line parade, a loose procession in which people dance down the street, often following a brass band. They can be impromptu or planned.
Outside the hospital, Leonard Temple teared up as he talked about a friend who was shot three times. Temple was told the man was hit while trying to push his own daughter out of the way.
"People were just hanging out. We were just chilling. And this happened. Bad things always happen to good people," said Temple, who was at the parade but didn't see the shootings.
Gang turf wars often root cause
Shootings at parades and neighbourhood celebrations have become more common in recent years as the city has struggled with street crime. Police say gang turf wars often are the root cause.
The neighbourhood where the shooting happened was a mix of low-income and middle-class row houses, some boarded up. As of last year, the neighbourhood's population was about 60 per cent of its level before Hurricane Katrina devastated New Orleans in 2005.
Police vowed to make swift arrests.
"We'll get them. We have good resources in this neighbourhood," Serpas said.