New Orleans ? Gunfire erupted among the crowd of people watching a popular Mardi Gras parade, killing a woman bystander and wounding three other people. Four teenagers were arrested Thursday.

Hundreds of people watching the Krewe of Muses parade stampeded to safety when they heard the gunfire Wednesday night, and some members of a high school band marching near the shooting dropped to the pavement.

Parade-goers help a woman who was among four people shot during the Krewe of Muses parade on St. Charles Avenue in New Orleans. Gunfire erupted Wednesday night among the crowd of people watching the popular Mardi Gras parade, killing one bystander and wounding three others. Four teenagers were arrested Thursday.

An argument among a large group of people apparently sparked the gunfire but the victims were all believed to be innocent bystanders, police Capt. Marlon Defillo said.

A woman, 20, died a short time after the shooting. A man and a woman with gunshot wounds were taken to a hospital, and another person, who was grazed by a bullet, refused treatment.

Police recovered two guns and at least a dozen bullet casings. Officers working the parade route were on the scene in seconds, Defillo said.

“There were six police officers 20 feet away from where this happened,” Defillo said. “These individuals were extremely brazen to pull out firearms in the presence of police officers.”

The suspects — Adrian Norris and Alvin Wilson, both 17, Ray Smith, 19, and a 15-year-old boy — face murder and attempted murder charges. The juvenile’s name was withheld.

The shooting happened during a parade by the Krewe of Muses, an all-female contingent.

The parade is part of the city’s Carnival season, a heavy tourist draw, that peaks with Mardi Gras or “Fat Tuesday” — a final day of revelry before Ash Wednesday — less than a week away.