Three people are dead and two others are in hospital after a person opened fire in a New Orleans gun shop, killing two before dying as customers and employees fired back police claim.

According to a statement from the Jefferson Parish sheriff's office, the shooting took place at the Jefferson Gun Outlet in the suburb of Metairie at about 2:50 pm on Saturday.

Sheriff Joseph Lopinto said the gunman hit two people inside initially, and then several other individuals opened fire on the shooter, both inside and outside the building, either employees or store customers.

In front of the outlet that faces the main thoroughfare through Jefferson Parish, guns and ammunition are sold. In general, customers who want to use the shooting range go around the building's side entrance. A sidearm is also worn by workers who work there.

Two other persons were also struck by bullets and were hospitalized in stable condition, Lopinto said. He said several gunmen were there, and investigators had just started trying to put together what had happened.

The sheriff said, "We're trying to put it all together, piece it together."

Immediately, none of the dead or injured were identified. The investigation continued as investigators sought to ascertain the precise specifics of what occurred, Lopinto said.

When both Tyrone Russell and Wanetta Joseph heard what they both described as rapid-fire, they were both in a conceal-and-carry course at the shop. They said the gunshots sounded much louder than the normal muffled shooting inside the shooting range that they are used to hearing.

"We heard gunshots and screams," Russell said. "They escorted us out when the police arrived. Everywhere, I could see glass. It was just like a scary scene really.

"It was extremely loud, almost like a bomb," said Joseph, who was hiding under a table with other students, not knowing if there were several shooters or whether one was near the classroom.

The students remained with one teacher, while two others fled the room and went for the sound of gunshots.

Russell said he could see a man "laid out" in the parking lot not far from his vehicle, which had been hit by bullets when he was led out. He reported seeing broken glass and casings of bullets strewn around the shop.

Caution tape surrounded the company in order to prevent onlookers from getting close to the scene where previously arrived ambulances and various law enforcement vehicles. A nearby Taco Bell was evacuated.

A man could be seen behind the yellow police tape outside the building shouting "Where is my son?" ”

Metairie is a major New Orleans suburb in neighboring Jefferson Parish, about five miles (8km) west of the city's famous French Quarter.