ST. CLOUD — Dahir Adan was a quiet and studious 20-year-old who came from a humble and well-known local Somali family.

But Saturday night, in an unexplained fit of rage, he put on a private security uniform, headed to the Crossroads Center mall in town and pulled a knife, slashing, stabbing and injuring 10 people before he was fatally shot by an off-duty police officer.

The stunning attack, in which Adan — a Somali refugee who moved to the United States with his family when he was 3 months old — reportedly referred to Allah and asked at least one victim whether they were Muslim, is being investigated as an act of terrorism.

Federal and local authorities are scrambling to find out whether Adan acted alone and what, if any, connection he may have had to any foreign terrorist groups. On Sunday, roughly 12 hours after the stabbings, a media agency for the Islamic State in Iraq and the Levant (ISIL) took to Twitter to claim credit for the assaults.

St. Cloud Police Chief William Blair Anderson said at a news conference Monday that investigators have yet to find evidence that Adan was radicalized or communicated with a terrorist group or acted with others. He also said that authorities have found nothing so far linking the stabbings to the weekend bombings in New York and New Jersey.

A spokesman for the FBI, which is working with St. Cloud police, said Monday that the agency could not yet provide new details in the case.

Early in the day, as President Obama telephoned Gov. Mark Dayton to express concern over the mall attacks and offer assistance, the mall reopened with increased security patrols working the entrances and lobbies and greeting subdued, but determined, shoppers.

A group of retirees clustered around a mall map, murmuring quietly as they compared what they'd heard about Adan's path as he slashed his way from Sears to Macy's. As security workers walked the corridors and circled the parking lot, other shoppers wandered the mall, looking at outfits or eyeglasses or the yipping toy dog leashed to a mall kiosk.

While many in this central Minnesota city of 66,000 people worked to re-establish routine, Adan's family and those in the Somali community who knew him struggled to make sense of Saturday night.

"We are in deep shock as everyone else is in the state of Minnesota," Adan's family said in a statement released by their attorney

The family expressed its "deepest sympathy and condolences" to those injured and affected by the attacks, adding that "we pray for their speedy recovery." It also urged residents to "stay united" and "not rush to judgment or conclusions" as investigators carry out their work.

Relatives said Monday night that they are focused on mourning Adan and organizing a private burial.

"This is shocking to everyone," said Mohamed Mohamud, a longtime neighbor of Adan's family who has known the Adans since they lived in Fargo, N.D. "This is a very humble family. This is a well-known family both here and in North Dakota."

Adan lived in an apartment in St. Cloud with his father, had attended classes as recently as last spring at St. Cloud State University, and had worked part time as a security guard at Electrolux Home Products, a local business, until this past June.

"This was the most assimilated kid," said Jama Alimad, a St. Cloud community leader and a friend of the Adan family. "He was an A student. He was a tutor. He was employed."

Two nights before the mall attack, Adan called his soccer coach, asking for weight loss advice.

"He wanted to lose 17 pounds," said Ahmed Ali, a Somali community soccer coach. Adan was a big guy, friends said — 6-foot-2 or 6-foot-3 and maybe 190 pounds. He always seemed calm, not aggressive, even on the soccer field. He kept to himself, the coach said, but didn't seem to be depressed or discouraged, although he confided to Ali that "he was sick and tired of sitting home and eat[ing]."

"Dahir wasn't a social guy. He wasn't a friendly guy who got to know everybody," Ali said. But "he was a good person. A person who dealt with people in a nice way. … He was more interested with school, work and losing weight."

Barakad Omar, a schoolmate, said Adan was the last person he'd expect "would do something like this."

"He was a good guy," Omar said, "An American kid."

Hudda Ibrahim, who teaches diversity and social justice at St. Cloud Technical and Community College, and who knows relatives of Adan's family, said: "We weren't expecting this in St. Cloud. … St. Cloud is a small city. We know each other. This is a good family."

In the wake of Saturday's attack, more than a dozen representatives of almost as many faiths gathered here Monday night to plead for unity, kindness and empathy.

"Many people are frustrated, many people are afraid," said Jaylani Hussein, of the Minnesota Council on American Islamic Relations. "But this community is resilient. This community is strong. … We will show the rest of the world that this tragedy will not break us."

Amid scattered reports of backlash against St. Cloud's Muslim community, the community has responded in the most Minnesota way possible, by asking people to politely stop doing that, said Natalie Ringsmuth of the group #UniteCloud.

In one case, a woman was boasting on Facebook about a group of trucks that were rolling through a Somali neighborhood, waving Confederate flags.

Ringsmuth said she reached out to the woman and explained that the display was scaring people. The woman, Ringsmuth said, promptly apologized and promised not to do it again.

While those who knew Adan searched for answers Monday, those who know the police officer who confronted him praised the officer's quick action.

Avon Police Chief Corey Nellis credited "divine intervention" with putting Jason Falconer, one of his most experienced officers and a part-time member of the small-town department who also owns a firing range and training facility, at the mall just as Adan began attacking shoppers.

"I am very proud of officer Falconer's heroic actions," Nellis told reporters at a news conference at Avon City Hall.

"Officer Falconer put himself in harm's way to protect the public from a man who had already stabbed [10] victims and would have very likely harmed more people, had [he] not acted so quickly."

Falconer, a competitive shooter who serves as a firearms instructor for the city, was uniquely qualified to respond to the crisis, Nellis said.

"If I was going to ask anybody to fire live rounds in a crowded mall, I would trust his abilities," Nellis said.

One of the people who crowded into the Avon City Hall to listen to the news conference was a woman who was working in the mall Saturday night. She and a customer dove to the floor, terrified, when they heard shots ring out.

"I am very thankful to Jason," said the woman, an Avon resident who did not want to be identified, but who knows Falconer as a familiar face around the small town of 1,400 people about 85 miles northwest of Minneapolis. "Number 1, for being there, but also for putting his life at stake for the rest of us."

The woman said that she's doing "OK" today, but "it is very nerve-racking. It is very scary. It makes you a little more frightened, a little more cautious. … It's in the back of your mind, always."

Staff writers Ricardo Lopez and Stephen Montemayor contributed to this report.