Three people are listed in serious condition after 19 were shot and wounded at a Mother's Day parade in New Orleans on Sunday, police said.
Most of the parade victims were grazed, including two 10-year-olds.
The FBI attributed the incident to "street violence," not terrorism.
The victims were in the "second line," the name for informal street parades that wind through New Orleans behind marching bands and dancers.
The idiosyncratic local tradition has sometimes stirred debate in the famed Louisiana city, particularly after violence has marred previous events.
"Just a very tragic day for us in New Orleans, especially on Mother’s Day," Mayor Mitch Landrieu said. “We have mothers that were shot, little children that were shot."
On Sunday, participants and onlookers were milling about on the streets and the sidewalks of east New Orleans' 7th Ward when shots rang out at 1:47 p.m.
A video uploaded to social media after the shooting took place appeared to capture the sounds of at least two guns, which police later confirmed.
Landrieu said there was no reason to believe the shooters were part of the parade.
Two participants said that the second line, which featured music, drinking and dancing, had veered off its planned route right before the shooting.
Mary Beth Romig, a spokeswoman for the FBI in New Orleans, told the AP that federal investigators have no indication that the shooting was an act of terrorism.
“It's strictly an act of street violence in New Orleans,” she said.
A "full contingent" of officers had been accompanying the procession and saw three men running away from the scene that were deemed suspects.
Many of the wounded were grazed by bullets and ricochets, Remi Braden, spokesperson for the New Orleans Police Department, said in a statement.
"At this point, there are no fatalities, and most of the wounds are not life-threatening," Braden wrote. "But all medical conditions are not known at this time."
"Victims were rushed to nearby hospitals. Detectives are conducting interviews, retrieving any surveillance video in the area and, of course, collecting all evidence."
Shermaine Tyler, 32, told the New Orleans Times-Picayune that she was at her home about a block from the second line when the shooting began.
"Me and Mom were going to the second line. I told her I didn't want to go because there are always shots at a second line," Tyler said afterward.
"And the second I heard shots, I heard shots fired, we ran outside and one man fell in my lap who had been shot." She said he'd been shot in his groin and hand.