Bergen County Prosecutor John Molinelli said the body of Richard Shoop, 20, of Teaneck was found in a back area of the Garden State Plaza mall in Paramus. He said Shoop killed himself with the same weapon he used at the mall and that a suicide note was found.
No other injuries were reported.
Searches of the Garden State Plaza mall are complete and there is no further evidence of explosives or weapons.
The mall will be open to retailers and their employees only beginning at 6:00 am so they can prepare their stores and collect any personal items left behind. The mall will be open for customers at 10:00 am, when all entrances will be available.
It will take weeks for toxicology reports to indicate if the gunman was under the influence.
Shoop had several magazines of ammunition with him. Authorities said the reason is unknown, but they will continue to examine his intentions.
Authorities will assess whether his weapon was fired more than six times.
Paramus police said Shoop's body was discovered around 3:20 a.m. Tuesday deep within a lower level of the mall that is not a public area.
The suspect's brother, Kevin Shoop, spoke to reporters outside the family home and expressed sympathy for the victims.
"My brother intended to harm nobody else but himself," Kevin Shoop said. "Just sadly, he decided to make an act of self-indulgence by taking his own life publicly. And it's a tragedy for us all."
The incident began when Shoop walked into the mall at 9:19 p.m., just before closing, wearing dark clothing and a motorcycle helmet and fired several shots into the air. The gunfire sent customers and employees scrambling for safety.
At 12:13 a.m., SWAT team officers in tactical gear could be seen shooting out the window of Neiman Marcus as they searched for the suspect.
Then, at 12:50 a.m., law enforcement officers raided Shoop's home, a few miles away on Emerson Avenue in Teaneck, where they found a suicide note. Authorities believe he stole a gun from his brother, then modified it to resemble an assault rifle. They believe that is the weapon found next to his body inside the mall.
"He does have a history of drug use and drug abuse, but we do believe the motive for what he did tonight was suicide, whether self-inflicted or, God forbid, suicide by cop, which no one ever wants to see," Molinelli said. "And it looked like that was his motive. At this time, based on what we know, it did not appear that he entered the mall to actually shoot anyone. And I say that because it appears that he did have ample opportunity to do that and chose not to."
There are reports that when police arrived at Shoop's home, they encountered a man holding a screwdriver who answered the door. Cops told him to drop it, and he apparently complied.
Authorities say Shoop worked at a nearby pizza place and was not a mall employee. He reportedly was a user of MDMA, the active drug in ecstasy and molly, among other drugs, and had a police record. He did not, however, have a history of mental illness.
Witnesses said the sound of gunfire sent customers and employees rushing hysterically for the exits and hiding places at the mall, which will remain closed on Tuesday. However, access will be allowed to the parking lot for those who need to pick up their vehicle. Please use the Route 17 Southbound entrance only.
Jessica Stigliano, 21, of Ridgefield, who'd been in the food court, told The Associated Press that she had thought, "Not many people run for their life, but that's what I'm doing right now."
Bergen County spokeswoman Jeanne Baratta told the AP that SWAT teams concentrated their search in the northeast corner of the 2.2 million-square-foot mall, near a Nordstrom store, believing the suspect might still be in the mall.
She said authorities found one bullet casing.
Hundreds of law enforcement officers converged on the mall, which was put on lockdown. New Jersey State Police landed a helicopter in the parking lot and SWAT teams with K-9 units went through the mall and evacuated anyone who was still there.
Nick Woods was working in the Lego store when a woman ran by shouting that there was a shooting.
Woods said his supervisor locked them in a back room, along with a man and a child who ran into the store. When they finally peeked out two hours later, he said they saw police officers standing outside and Woods called 911 to ask that the officers be told they were coming out.
He said the emergency operator told him she couldn't contact individual police officers and that he should walk out with his hands in the air.
"I had to go out of the store shouting at the officers with my hands up, and they turned and pointed their guns at me," Woods said. "It was one of the scariest experiences of my life."
Joel Castaneda, 18, of Englewood, who was working at the Ann Taylor Loft store, also spent time locked in a back room. He said he heard several loud bangs and thought they were from construction at the mall, but then saw people running.
He said people rushed into his store and they locked themselves in a back room - employees and customers alike - where they pulled out cellphones to try to get news or reach loved ones.
Carlos Sinde, 36, of Queens, was alerted by fire alarms going off while he was watching previews for the 9:20 p.m. showing of the movie "Gravity" at the mall.
He said he walked into the mall where someone was saying "I think there was a shooting," but he didn't take it seriously. Then, security guards ran up, urging customers to leave. He said one security guard was crying.
"Once the security guards started telling us what was going on, that's when there was hysteria," he said.
Early Tuesday, families were being escorted by police to a Chili's restaurant on the outskirts of the mall area to be reunited with others who had been in the mall for hours.
Althea Brown, 26, of Paterson told NorthJersey.com she was in a clothing store when she saw a man walk by and then heard three shots followed by two more. She said he appeared to be wearing body armor and was wearing a helmet with the visor pulled up.
Najde Waters, who works in customer service at H&M, said when they heard shots his manager and store workers followed an action plan they'd rehearsed for just such a scenario.
"We all prepare, like schools do. We have a plan where we all meet up in the back of the store and if we can exit together out the front we do, but in this case we had to exit out the back," Waters said.
He said they went to their meeting place near a light pole.
The mall, which has more than 270 stores, is located about 15 miles northwest of Manhattan.
(The Associated Press contributed to this report)