Shoppers hit the ground running at Roosevelt Field Mall in Garden City Sunday thinking there was an active shooter.

In a video posted on social media, parents can be seen running with children outside in apparent confusion and fear.

Nassau County police tell News 12 they are increasing patrols in and around the mall as a result of the incident.

Police say a 21-year-old male was hit in the face by someone who ran from the scene. That caused massive panic at the mall and many people thought there may be an active shooter incident.

However, detectives tell News 12 no shots were fired.

Don Longo, a subject matter expert in active shooter incidents, says people in the mall did the right thing by leaving.

"We want to see people reacting immediately because time is a huge factor," Longo says.

He urges people to be situationally aware at all times, know the exits, know who is around and look for a place to take cover if it is too dangerous to get to an exit.

The 21-year-old man was taken to a local hospital for treatment.

"It's really frightening and you know I was shaking," said Pia Grace Lapay, of Glen Cove.

The incident follows a shooting at the Green Acres Mall where a person was shot in the leg and others were sent fleeing.

Police say a chair hitting the ground was likely what so many people thought sounded like a shot fired.