SALT LAKE CITY - The FBI said Wednesday it has no reason to believe the shooting spree that killed five people in a shopping mall was an act of Islamic terrorism, leaving a young Bosnian immigrant's motives a mystery.

"It's just unexplainable," FBI agent Patrick Kiernan said. "He was just walking around and shooting everybody he saw."

Sulejman Talovic, 18, fired randomly at shoppers Monday, killing five and leaving four others with bullet wounds before he was shot dead by police.

Authorities are investigating how Talovic acquired one of his weapons, a .38-caliber pistol, which is illegal for a teenager to possess, said Lori Dyer, in charge of the local office of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives.

Those efforts were delayed Wednesday when an East Coast storm shut down ATF offices, she said.

Talovic was heavily armed with ammunition, a shotgun and a .38-caliber pistol.

"You can buy long guns at 18. That's not a problem. The handgun he shouldn't have had, so obviously we're going to look at where he got that gun," Dyer said.

Meanwhile, less than 48 hours after the slayings, police tape was removed from the parking lot and Trolley Square reopened, although it was up to each shop whether to resume business.

Workers repaired pillars damaged by shotgun blasts and replaced broken windows with plywood.

"We're opening the mall, not in the sense of business as usual but to let the healing begin," said Tom Bard, an executive at Scanlan Kemper Bard Cos. of Portland, Ore.

A card store called Cabin Fever won't reopen until Feb. 21, but the owner offered free Valentine's Day cards outside the door. The sign said: "Don't forget to tell someone you love them today."

John and Amanda Redford of Ogden, in town to celebrate their second wedding anniversary, walked around the mall.

"Just curious," John Redford said. "It's pretty weird to know that it just happened a couple of days ago."

Salt Lake City Police Chief Chris Burbank said the rampage could have been even worse if not for the quick actions of an off-duty officer from Ogden, Ken Hammond, who engaged Talovic in a shootout before other officers arrived.

Talovic wanted to "to kill a large number of people," Burbank said Tuesday.

Investigators knew little about Talovic, except that he lived in Salt Lake City with his mother. He was enrolled in numerous city schools before withdrawing in 2004.

He was a legal U.S. resident, arriving with family members as war refugees in 1998, said Virginia Kice, a spokeswoman with the U.S. Immigration and Customs Enforcement.

Talovic was only 4 when he and his mother fled their village of Talovici on foot after Serbian forces overran it in 1993, people close to the family told The Associated Press.

He lived as a refugee in Bosnia from 1993 to 1998, when his family moved to the United States, they said.

During that period, he spent some time in Srebrenica, the northeastern enclave where up to 8,000 Muslim men and boys were slaughtered in 1995 by Serb forces.

Talovic left Srebrenica two years before the massacre, but acquaintances suggested it may have left an indelible mark on the quiet little boy they knew.

"That's why I'm convinced the war did this in Utah," said Murat Avdic, a friend of the family. "There cannot be any other reason."

Four people who were shot at the mall remained were in hospitals, two in critical condition and two listed as serious.