Gunshots and then screams erupted in a French Quarter crowd celebrating the countdown to Mardi Gras, and police who released a bystander's video footage early Sunday said four people had been wounded in the Bourbon Street shooting after an argument involving some of the revelers.

Four shots rang out rapidly amid the throng, followed by the screams also heard on the videotape released by police. Authorities did not immediately say if any arrests had been made. They appealed for the public's help in their investigation of the shooting Saturday night on the famed French Quarter street.

Those wounded included a male victim in guarded condition with shots to the abdomen, thigh and pelvis area along with one other male and two female victims with lesser gunshot wounds, New Orleans Police spokesman Frank B. Robertson said in a statement Sunday.

The other gunshot victims included a male struck in the buttocks, a female hit on the chin and the bottom of the right foot and another female struck on a toe, police added.

Police had said late Saturday that the most severely wounded male was in critical condition and had been sent into surgery while the others were in stable condition. None were identified by age or name.

The shooting came on the frenzied last weekend of partying before Mardi Gras, French for the Fat Tuesday celebration that is the signature tourist event of the year in New Orleans, marked by big crowds.

Tourism is a lifeblood industry for New Orleans and Mardi Gras is one of the city's leading events along with Jazz Fest and major sporting events such as the recent Super Bowl. New Orleans also remains plagued by violent crime, including gun violence that has soared in the years since Hurricane Katrina devastated the city in 2005.

The bystander's footage showed many partying in costumes, several apparently with drinks in hand, before the shooting.

Police said that two men initially were arguing with a male victim who ended up the most seriously wounded. According to police, the two suspects briefly withdrew after the initial argument, then one of them returned with a third man and the shooting erupted.

Authorities described the three as "perpetrators" and said one appeared to be about 18 to 22 years old, another about 20 to 25 and a third as a man with a heavy build and beard. Police gave no further information about them or their whereabouts.

Patrick Clay, 21, a Louisiana State University student, told The Times-Picayune he was standing on the corner of Bourbon Street when suddenly he saw a crowd running and people screaming that there had been a shooting.

"Everyone immediately started running and the cops immediately started running toward where people were running from," Clay said. "I was with a group of about seven people and at that point we all just kind of grasped hands and made our way through the crowd as soon as possible."

Some bartenders and revelers said the block of Bourbon Street where the shooting occurred was closed off to the crowds for a time while detectives investigated. Some of the visitors hunkered down in nearby bars before partying resumed in force hours later across that stretch of Bourbon Street.

Andrew Pittman, 20, of Auburn, Ala., said it wasn't his first Mardi Gras after attending one last year, but it was his first time near a shooting site. "We were just walking down Bourbon Street, and people walked by and said there was a shooting. We saw like 12 cops on horses, so we just turned around."

Julia Rosenthal, a 19-year-old visitor from Westchester, N.Y., had mixed feelings about hanging out in the French Quarter after the shooting. "It's not an OK thing that happened, and it's definitely scary. But I'm not going to let it affect my night," she told AP.

Peter Manabani, an employee at the Rat's Hole bar, said police had shut down a whole Bourbon Street block for an hour to investigate but allowed people to return to the area later.

Hours later on Sunday, there was little evidence that a shooting had occurred. Late-night revelers drank and cavorted in full party mode, packing the block amid a heavy police presence.

Laura Gonzalez, 21, of Baytown, Texas, said it was her first Mardi Gras and she spent some time in the Fat Catz bar nearby as police investigated. She said the bar locked its doors quickly after the shots rang out and wouldn't let anyone in or out while police went to the scene.

Asked if it was frightening, she responded: "Not really. We were just locked in a bar and we weren't going to let this one incident wreck our party."

Parades rolled all day Saturday but none on Bourbon Street because the streets are too narrow. One of the biggest Mardi Gras parades, the Krewe of Endymion, rolled down New Orleans' major Canal Street and just skirted Bourbon Street a few hours before the shooting. Typically, once the parades end, partygoers head to the French Quarter.