The gunman was identified as Richard Shoop, 20. The authorities said his body was found in the mall at around 3.20am local time. He had a self-inflicted gunshot wound.
He entered the Westfield Garden State Plaza Mall on Monday night and fired his weapon at least six times, ABC News quoted the authorities as saying. The police described the weapon as a rifle, and also added that Shoop had a suicide note.
No other injuries have been reported so far.