CLACKAMAS, Ore. -- The authorities said on Wednesday that the gunman who fatally shot two people at an Oregon shopping mall before killing himself sprayed dozens of rounds from a semiautomatic rifle and had been carrying several magazines filled with extra ammunition during the attack amid thousands of holiday shoppers.
The gunman, identified as Jacob Tyler Roberts, 22, was also wearing what the authorities called a "hockey-style mask" and was outfitted with a load-bearing vest, which allowed him to carry more ammunition.
Sheriff Craig Roberts, of the Clackamas County Sheriff's Office, said Mr. Roberts had no known connection to his victims and had apparently fired randomly with an AR-15 rifle.
"We don't understand the motive for this attack," said Sheriff Roberts, who called the shooting a "horrific act of violence."
The dead were identified as Steve Forsyth, 45, a youth sports coach who owned a small business in the mall, and Cindy Ann Yuille, 54, who was apparently shopping.
A third person, Kristina Shevchenko, remained hospitalized in serious condition with at least one bullet wound, the authorities said. Her age was not released.
Mr. Roberts had no known prior criminal history, the authorities said, although the AR-15 he used in the shooting had been recently stolen from someone Mr. Roberts knew. The theft had been reported on Tuesday, hours before the attack.
By interviewing witnesses and viewing the surveillance tapes, the authorities say they now know that on Tuesday afternoon, just before 3:30 p.m., Mr. Roberts had parked his car, a 1996 Volkswagen Jetta, in a spot near an entrance to the sprawling Clackamas Town Center mall's food court. He walked hurriedly inside with the assault rifle in hand.
As people in the food court ate, he opened fire, though it was unclear if any of the dead had been in the food court or if they had been able to flee in time.
Mr. Roberts next moved quickly through the mall, though at one point the weapon jammed, the authorities said. He was able to clear the rifle and begin calmly firing again -- as many as 60 rounds.
He killed himself in a mall corridor, the authorities said.
Sheriff Roberts said searches were conducted at Mr. Roberts's home in Portland and on his car, which was found in the parking lot of the mall. Sheriff Roberts declined to discuss what the searches may have turned up.
The police have said that none of the more than 100 law enforcement officials who responded to the popular mall on Tuesday had fired a shot.
At least 10,000 people were in the mall at the time of the shooting, the police said.
There have been a number of shootings in public places across the country in recent months. In October, a gunman opened fire at a day spa in a Milwaukee suburb, killing three women, including his ex-wife, before killing himself. In August, in another Milwaukee suburb, a self-proclaimed white supremacist killed six people at a Sikh temple before being killed by the police. Two weeks before that, a gunman killed 12 people and wounded 60 in an attack on a movie theater in Aurora, Colo.
Timothy Williams and Michael Schwirtz contributed reporting from New York.
This article originally appeared in The New York Times.