BBCTen people have been killed and 35 injured after a man intentionally drove into a crowd in New Orleans and then began firing a weapon, police have said.
Police chief Anne Kirkpatrick said the attacker drove a pickup truck along Bourbon Street "very fast... trying to run over as many people as he could" at around 03:15 (09:15 GMT). He crashed, then shot and injured two police officers.
The FBI said in a statement it is "working with our partners to investigate this as an act of terrorism". The suspect is dead, the agency added.
Kirkpatrick said the man was "hell-bent on creating the carnage and the damage that he did". One witness said he "walked past dead and injured bodies" in the street.
He said "people started running and getting under tables like it was an active shooter drill".
Watch: New Orleans police brief media on Bourbon Street attack
A CBS reporter saw multiple people with injuries on the ground at the intersection of Bourbon and Canal streets.
A video confirmed as genuine by BBC Verify shows a person lying on the ground and a crowd scattering as what appear to be gunshots are heard. Another shows two injured people lying in a street.
Whit Davis, from Shreveport, Louisiana, told the BBC that he had been in a bar in the Bourbon Street area when the attacker struck. He did not hear the crash and shooting as the music was too loud.
"People started running and getting under tables like it was an active shooter drill. Then the police held us in the bar for a while and when we were finally allowed to leave we were walking past dead and injured bodies all over the street," he said.
"Everyone was just completely in shock," he added. "I visit New Orleans frequently and have never seen anything close to this bad."
FBI Special Agent Althea Duncan, who is leading the investigation, said an improvised explosive device was also found at the scene and they were working on confirming whether it was "viable".
US President Joe Biden had been briefed "on the horrific news", according to a White House statement.
"The FBI is already on the ground supporting local law enforcement in the investigation and the president will continue to be briefed throughout the day," the statement read.
Jim and Nicole Mowrer, who were visiting New Orleans from Iowa, told the BBC's US news partner CBS that they were in the French Quarter when they heard crashing noises down the street.
They said they saw a white truck slam through a barricade "at a high rate of speed", then heard gunshots after the crashing noises.
"We stayed in the alcove until the gunfire stopped, came out into the street, and came across a lot of - several people who had been hit, [we] wanted to see what we could do to help," Nicole said.
They tried to help people they found wounded, but realised the victims had died. They said the truck hit people only about a block away from where they were walking.
The couple said the victims they saw had injuries from the truck impact, and they did not see any apparent gunshot wounds. They said they left the area once emergency responders started arriving.
An unnamed man was working in a nearby hotel when he heard "loud banging sounds" a little bit before 03:20 local time.
"We were in our room just pretty much closing down for the evening at the end of all the events and everything and when we looked out the window we noticed there was a lot of bodies lying on the ground," he told CBS News.
"The truck was speeding away. I immediately ran downstairs to see if there were some people I can help out and unfortunately some people did perish during that event."
He said they put other people into the hotel for assistance.
"The scene was just horrific," he said.
Initial reports seem to indicate that a majority of the victims were locals, police said.
Louisiana Governor Jeff Landry said in a post on X that he was "praying for all the victims and first responders on scene".
"A horrific act of violence took place on Bourbon Street earlier this morning," Landry wrote.