Updated 5:25 a.m. ET
PARAMUS, N.J. A gunman fired at least six rounds into an escalator before taking his own life, authorities said.
Bergen County, N.J. prosecutor John Molinelli told reporters early Tuesday the body of Richard Shoop, 20, of Washington Township, N.J., was found behind a construction storage area of the Westfield Garden State Plaza Mall in Paramus.
It doesn't appear Shoop entered the mall to shoot anyone because had ample opportunity to but didn't, Molinelli says, adding that Shoop's motive seems to have been self-inflicted suicide or suicide-by-police - ending his life at the hands of officers.
Molinelli says Shoop's family told police Shoop had a history of drug abuse, and relatives believe MDMA was his drug of choice.
A note was recovered at Shoops' home, Molinelli says, but authorities aren't calling it a suicide note or disclosing its content.
Shoop's body and the gun were still at the scene early Tuesday, Milinelli said. The weapon looks like an AK-47 assault rifle but may have been a modified handgun.
Shoop appears to have stolen it from his brother, Molinelli said.
Shoop wore a black outfit with a black motorcycle helmet, and fired the rounds into an escalator.
Shoppers and mall workers, who'd hid in stores and anywhere else they could when the shots rang out, were leaving throughout the night via a Chili's restaurant at a parking lot adjacent to the mall. It was unlikely any were still in the mall, Molinelli said.
The mall was to be closed Tuesday.
A woman who works at a store in the mall told CBS New York station WCBS-TV she saw a man carrying a rifle.
"I saw him walk past our door, and he paused for a second and just looked inside the store, and he fired two more (shots)," she said. "He was all dressed in black from head to toe with a helmet, I would say with a motorcycle helmet. I just froze. I didn't want to run, because he might maybe come after me. I just stood there."
A witness tweeted that the shooting occurred by Nordstrom department store on the second floor.
"As I was closing the store, I heard these loud fire-cracking noises. I never heard a gunshot before," an employee at the Michael Kors store who gave his name as Adam told WCBS radio. "I had a customer that shopped before, and she was running back into the store and saying, 'Someone has a gun.' So automatically, I ... started locking the gate and told the staff to go to the back with the customers even in the store."