Witnesses said the gunman fired down on shoppers from a third floor balcony of the Von Maur store. Police recovered an SKS assault rifle believed to have been used by the gunman.
The young shooter, identified by police as 20-year-old Robert A. Hawkins of Bellevue, Neb., left a suicide note which included the grim prediction: "Now I'll be famous."
Police have not said anything about the motive, if it is in fact known to them. But Hawkins had suffered a string of setbacks over the past year. A family friend says he recently broke up with a girlfriend and got fired, and a source tells CBS News affiliate KMTV that he tried, but failed, to get into the Army.
According to Sgt. Teresa Negron, police received a 911 call from someone inside the mall, and shots could be heard in the background. She says by the time officers arrived - six minutes later - the shooting was over.
"We sent every available officer in the city of Omaha," said Negron, who did not know whether the gunman said anything during the rampage to hint at a motive.
The Omaha World-Herald reported that the gunman had a military-style haircut and a black backpack, and wore a camouflage vest.
"My knees rocked. I didn't know what to do, so I just ran with everybody else," said Kevin Kleine, 29, who was shopping with her 4-year-old daughter at the Westroads Mall, in a prosperous neighborhood on the city's west side. She said she hid in a dressing room with four other shoppers and an employee.
Authorities say Hawkins was found dead on the third floor with an apparently self-inflicted gunshot wound, and his victims were discovered on the second and third floors.
Hawkins dropped out of Papillion-La Vista High School in Papillion, Neb., in the spring of 2006 and was kicked out by his family that same year.
After staying at the homes of a number of friends for a few days at a time, he wound up moving in with the family of surgical nurse Debora Maruca-Kovac, who with her husband, took in Hawkins, a friend of her two teenaged sons.
"When he first came in the house, he was introverted, a troubled young man who was like a lost pound puppy that nobody wanted," Maruca-Kovac said.
Hawkins, according to Maruca-Kovac, was not on any medication for mental illness, but he had been treated in the past for depression and attention deficit/hyperactivity disorder.
"He was depressed, and he had always been depressed," Maruca-Kovac said. "But he looked like he was getting better."
"He was a very helpful young man, but he was quiet," Maruca-Kovac said. "He didn't cause a lot of trouble. He tried to help out all the time. He was very thankful for everything. He wasn't a violent person at all."
Hawkins, she said, was gentle and loved animals, liked music and video games, but had a drinking problem and would occasionally smoke marijuana in his bedroom.
Maruca-Kovac says Hawkins recently suffered two new setbacks, breaking up two weeks ago with his longtime girlfriend, and earlier this week, getting fired from his job at a nearby McDonald's.
At 1 p.m. Wednesday, he called Maruca-Kovac, telling her that he'd left a note for her in his bedroom. She says she tried to get him to explain, but he hung up.
Maruca-Kovac then called Hawkins' mother, who went to the Maruca-Kovacs' house and retrieved the note, which she took to authorities.
In the note, Hawkins wrote that he loved his parents and other family members, was "sorry for everything," would no longer be a burden to them, wanted his mom to have his Jeep, and his friends to have "whatever they want."
Maruca-Kovac did not hear about the shooting - which a witness said began around 1:50 p.m. - until she arrived at work at Nebraska Medical Center, where she saw patients being wheeled in.
"I had a feeling it could be him," said Maruca-Kovac, who had read the note before turning it over to his mother.