A worker at Roosevelt Field mall was shot and seriously wounded by a stray bullet fired during a robbery Tuesday at an upscale watch store, officials said. The shooter was in custody.

Shoppers described pandemonium and chaos inside the mall when the shot rang out. Fearing the worst, some of them ducked into stores, where workers closed the security gates.

“The motive was clearly a robbery,” acting Nassau Police Commissioner Thomas Krumpter said. “This was not an active shooter.”

Nassau County Executive Edward Mangano said the suspect entered the Rolex area of the Tourneau store at about 1 p.m. and attempted to rob it. As he tried to exit, the robber struggled with store security and his handgun went off, officials said.

Mangano said a 67-year-old mall employee in the corridor outside the store was struck by the stray bullet. He was hospitalized in serious but stable condition, Mangano said.

The suspect, who fired one shot, was arrested and the gun was recovered, Krumpter said.

Police are investigating to determine whether there are any other suspects. They declined to identify the suspect in custody.

NYPD Insp. Kenneth Lehr, 49, commander of the fugitive enforcement division, said he was at the mall doing Christmas shopping when he heard the shot. Lehr said he saw a stampede of people running away from the direction of the shot, so he ducked into the vestibule of a store and waited for crowd to clear.

“I thought for sure it was going to be an active shooter situation,” Lehr said, and as the corridor cleared he saw a struggle about 20 to 30 yards away. “It was a wrestling match, basically, for the firearm.”

Two uniformed Roosevelt Field security guards and a man in a suit — a security guard in the watch store who was a retired NYPD cop — struggled with the suspect, Lehr said. Handcuffs dropped to the floor, Lehr said, and he picked up the cuffs and helped secure the suspect.

“I don’t want to make this sound like I did anything alone,” Lehr said. “The heroism was on the part of that security person, the retired detective, what he did was remarkable; the two security guards, they are not armed, they raced into that store, they were there before me. I simply helped them close the deal.”

Lehr said he had a firearm with him in his holster but that he did not pull it out.

After the shooting, the Garden City mall remained open, though the crime scene in the Neiman Marcus wing was closed to the public, Mangano said.

A spokesman for the mall, owned and operated by Simon Property Group, declined to comment. The mall, which has more than 250 retailers, has been undergoing a $200 million expansion and renovation.

The shooting came on one of the last shopping days before Christmas. There was “a significant number of people” in the mall and near the store at the time, Krumpter said.

Shoppers said panic ensued after the shot was fired, as people evacuated.

“People were just running; it was chaos,” said Ava Doshi, a Macy’s employee who heard the gunshot. “I was just scared. I just wanted to get out.”

Mark Smith, who was shopping in the Bose audio store at the time, said he saw a “stampede” of hundreds of people running. “I heard a popping sound and I heard what sounded like a stand falling down or glass shattering.”

Smith, 47, of Roslyn said Bose store employees closed the store’s gate and he and other shoppers hid in the back room for more than an hour. “It was very scary,” Smith said.

Reaction to the shooting was reminiscent of one that occurred on Sept. 25, 2013, when frightened shoppers and others in the Roosevelt Field area sought refuge as police hunted for an armed man who had fatally shot a worker at a nearby business.

In that shooting, police said that Sang Ho Kim, 63, a vendor for Savenergy Inc., a lighting efficiency company near the mall, walked into its offices and shot and killed a worker and seriously injured the owner in what police said was a soured business relationship.

Lockdowns rippling from the shooting scene that day unnerved hundreds huddled inside the mall, which was closed to shoppers for close to four hours; public schools; a day care center; and Nassau Community College.

A manhunt ensued, with Kim found dead close to a week later, floating on the Hudson River near the Bear Mountain Bridge.

With Anthony M. Destefano and Laura Blasey