Updated at 6:58 p.m. 

Several hundred theatergoers watching “Skyfall” in South Minneapolis Saturday abruptly headed for the exits after a peculiar sulfuric odor filled the room during the film’s final minutes.

The source of the smell remains a mystery — some heard it was a prank smoke bomb — but it sparked a mass exodus that may have been stoked by lingering fears from recent mass shootings. A manager of the Riverview Theater in the Longfellow area said a majority of the 600 people who were packed into their massive auditorium exited into the cold night.

“When I smelled that smoke, I thought it was a gunshot,” said Justin Eibenholzl, who was watching the film with his girlfriend. “And I didn’t know anything other than we shouldn’t probably be in here.”

It began when people in the middle row stood up and turned around, Eibenholzl said. People then started grabbing their children and rushing toward the exits, as the gunshot-filled audio track of the film’s climax blared over the speakers. Someone in the aisle, not an employee, waved their hands and said, “Everyone out,” he recalled.

Laura Scher, a former Star Tribune employee who is now a freelance photographer, was sitting in an upper row with her three children. When the smell reached them, she said, “Every[one] panicked. ‘There’s smoke! Get out!’ And people were screaming and yelling.”

The Riverview’s manager, Loren Williams, described it as “a situation where everybody sort of played follow the leader.” Williams said he could not smell or see any smoke when he entered the theater minutes later. The fire department arrived, but soon left.

The voluntary evacuation could have been stirred by recent incidents, such as the mass shooting that took place in the opening minutes of “The Dark Knight” in Colorado last year. “The fact that there’s been incidents happening,” Williams said, “people just sort of act now and question later.”

A firefighter told Scher that he had heard it was a smoke bomb.

Scher said she was disappointed that no staff members directed the crowd and that it took several minutes for the theater to turn on the lights. She also feels firefighters should have spent longer reviewing the scene.

“I was so unhappy with the way that it was handled,” Scher said.

Williams responded that, based on security camera footage, the lights were turned on within 45 seconds of people standing up. He added that there was no yelling. “I’ve got a number of emails from people who were impressed by the orderliness. People were calm. It was not a mass confusion,” Williams said.

The Riverview was playing Skyfall, which was released last November, because it is an intermediate-run theater that shows films after their initial run for a reduced price. Tickets were $3.

Photo: A capacity crowd watching the presidential debates at the Riverview in 2004 (Carlos Gonzalez)