Chaos erupted at the mall in the Meadowlands Sports Complex after the bleeding victim walked into the mall shortly around 5:50 p.m., they said.
The victim was conscious when taken to Hackensack University Medical Center with serious injuries, sources with knowledge of the shooting told Daily Voice.
"Based on the preliminary investigation, detectives determined that only one suspect shot the victim, and detectives believe this to be an isolated incident," New Jersey State Police Trooper Brandi Slota said shortly after 11:30 p.m. "There is no threat to the public, and the incident remains under investigation."
She didn't elaborate.
"The American Dream Mall plans to reopen tomorrow [Friday] for regular operating hours," Slota said.
The mall remained locked down as tactical teams cleared it store by store and room by room -- including a storage room where 100 or so people had sheltered themselves with an off-duty police officer.
Troopers escorted patrons and employees out, Slota said.
State Police sent their SWAT team along with troopers. Joining them and East Rutherford police was a Bergen County Regional SWAT team and members of other area law enforcement agencies.
It was nearly 24 hours earlier that two men fled in a vehicle with New Jersey license plates after firing shots and frightening shoppers at the Roosevelt Field mall on Long Island.
SEE: Pair In NJ Vehicle Wanted For Firing Shots, Forcing Lockdown At Mall On Long Island
Thursday's shooting occurred the same day that the mall announced it will stage live concerts by artists including Ludacris through a multi-year deal with Live Nation. Tickets are scheduled to go on sale on Ticketmaster.com at 10 a.m. Friday, April 8.
In addition to concerts, the mall said it will have "unique live experiences like fan-to-artist activations, pop-up shops, launch parties for new music releases and upcoming tours, and more."
Click here to follow Daily Voice Ridgewood and receive free news updates.