The gunman who killed two people and then himself in a shooting rampage at a US mall packed with Christmas shoppers was 22 and used a rifle stolen from someone he knew, authorities said.
The fact that the rifle jammed and shopping centre employees were trained for the possibility of a mass shooting prevented a higher death toll in the incident in Portland, Oregon, they said.
Jacob Tyler Roberts had armed himself with an AR-15 semi-automatic rifle and had several fully loaded magazines when he arrived at the mall, said Clackamas county sheriff Craig Roberts.
The sheriff said the rifle jammed during the attack, but the gunman managed to get it working again. He later shot himself. The sheriff said authorities did not yet have a motive.
The gunman, who wore a mask, fired randomly, investigators said.
Employees at the shopping centre had been trained to run and hide, lock down and evacuate. Since previous mass shootings elsewhere in the US, the first police officers on the scene were trained to form teams and go inside instead of waiting for speciality teams. "This could have been much, much worse," said Sheriff Roberts.
Two people - a 54-year-old woman and a 45-year-old man - were killed, and another woman, Kristina Shevchenko, whose age could not be confirmed, was wounded and in a serious condition.
A law enforcement official told the Associated Press that the gunman did not have a criminal record.
The shooting started shortly after a man in a white mask carrying a rifle and wearing a bulletproof vest said "I am the shooter" as if announcing himself, said Austin Patty, 20, who works at a department store. A series of rapid-fire shots followed as Christmas music continued to play. Mr Patty said he ducked and then ran.
Witnesses said the suspect fired several times near the mall food court until the rifle jammed, and he dropped a magazine on to the floor and ran into the Macy's store.