(CNN) -- A 19-year-old gunman who killed eight people and then himself Wednesday at the Westroads Mall in Omaha, Nebraska, left a suicide note, police said.
Police have identified the gunman as Robert A. Hawkins, 19, of Nebraska.
Five other people were injured, and two of them were in critical condition, hospital officials said.
Chief Thomas Warren of the Omaha Police Department called the shooting "premeditated," but said it "appears to be very random and without provocation."
Surveillance cameras may have captured the shooting, Warren said.
"We'll be here throughout the night; it's a very extensive crime scene," he said.
Police identified the gunman as Robert A. Hawkins of Nebraska.
They have recovered an SKS assault rifle and the suspect's vehicle.
Debora Maruca Kovac, Hawkins' landlord who found the suicide note, said he wrote he was sorry for everything and did not want to be a burden to anyone any longer. Watch landlord describe phone call from shooter »
Hawkins said in the note he loved his friends and family, but "he was a piece of s--- all his life, and now he'll be famous," she told CNN.
She said Hawkins was a friend of her sons and "reminded me of a lost puppy that nobody wanted."
He came to live with her about a year and a half ago, telling her he could not stay with his own family because of "some issues with his stepmother and him."
She described Hawkins as well-behaved, although "he had a lot of emotional problems, obviously."
The shootings began about 1:42 p.m. Seven people were found dead at the scene by officers arriving six minutes later; two others, a male and a female, died after being transported to Creighton University Medical Center, said Fire Chief Robert Dahlquist.
A Creighton spokeswoman said a second female was undergoing surgery and was in critical condition Wednesday afternoon.
Three other people were taken to the University of Nebraska Medical Center. One, a 61-year-old man who sustained a chest wound after being shot in the armpit, underwent surgery and remained in critical condition in the intensive care unit Wednesday night, said hospital spokeswoman Maggie O'Brien. Learn more about the victims »
The other two -- a 34-year-old man who was shot in the arm, and a 55-year-old man who fell and struck a clothing rack as he was trying to escape -- were treated and released, she said.
Maruca Kovac told CNN that Hawkins left home Wednesday about 11 a.m., and called the house about two hours later, sounding upset.
"He just said he wanted to thank me for everything I'd done for him ... and he was sorry," Maruca Kovac said. He told her he had gotten fired from his job, she said.
"I said, 'Come home and we'll talk about it,' " she said. "He said, 'It's too late.' He said he'd left a note explaining everything."
Witness Jennifer Kramer told CNN she heard at least 25 shots. Watch witnesses describe the ordeal »
"He just kept firing," she said. She said she called 911 on her cell phone, whispering into it out of fear of being heard. A dispatcher told her other calls had been received and help was on the way, but she said it seemed to take "a long time" for them to arrive.
"It was just so loud, and then it was silence," she said. "I was scared to death he'd be walking around looking for someone else."
She said as she was being escorted out by police, she saw a man lying injured by the escalator where she had been previously.
"All of us were slightly confused because we didn't know what it was," said mall employee Charissa Tatoon about the first burst of gunfire.
"Immediately after that, there was a series of maybe 20 to 25 more shots up on the third floor.
"I was in the women's shoe department and there was a gentleman coming down the escalator that was very near the shoe department, and he was heard saying that he was calling 911, and immediately after that, the shooter shot down from the third floor and shot him on the second floor."
Warren, the police chief, said the victims included five females and three males, not including Hawkins. "We believe there was one shooter, and one shooter only," he said.
Maruca Kovac said she was unaware Hawkins had any guns, although she said he knew a lot about them, as did his stepfather. "When he first came to live with us, he was in the fetal position and chewed his fingernails all the time," she said.
But she said she thought he was improving, as he had gotten a job, a haircut and a girlfriend. However, she said Hawkins and his girlfriend had broken up in the last couple of weeks, and he had taken it hard.
She said late Wednesday that authorities were searching her house for evidence.
"My kids are devastated," she said. "We're all in shock."
Hawkins' former school district released a photo of a youth with glasses and long black hair. A spokeswoman said he attended Papillon-La Vista High School until he withdrew in March 2006.
Witnesses described chaos and frantic shoppers running away from the Von Maur store, where the shooting began just before 2 p.m.
"You're in such shock, it's hard to think. I was hoping God would spare us," said a woman who was clutching a rosary in her trembling hand after the shootings. "We had to put up our hands and follow the police to the outside."
Others described scenes of horror as they fled the mall. See a map of where the shooting took place »
Some shoppers and mall employees hid in clothes racks, dressing rooms and bathrooms after hearing the shots.
Most of the victims were shot inside the Von Maur store, Sgt. Teresa Negron said. Watch police talk about the shooting »
President Bush had visited Omaha Wednesday before the shooting.
"The president is deeply saddened by the shootings in Omaha, Nebraska, earlier today," White House press secretary Dana Perino said.
"His thoughts and prayers are with the victims and their families this evening. Having just visited with so many members of the community in Omaha today, the president is confident that they will pull together to comfort one another as they deal with this terrible tragedy."
As news of the shooting spread, people gathered outside the mall, checking on loved ones who were inside.
The shopping center will be closed until at least Thursday, police said.
The shooting was at least the fourth at a mall or shopping center so far this year, following incidents in Salt Lake City, Utah; Kansas City, Missouri; and Douglasville, Georgia. E-mail to a friend