COLUMBUS, Ohio — The official news agency of the Islamic State labeled the Ohio State student who smashed his car into a crowd and then slashed at people with a butcher knife a “soldier” of the militant group, according to an organization that monitors extremists.

This posting does not necessarily mean that Abdul Razak Ali Artan acted at the behest of the terror group, which often claims responsibility for attacks in which it had no actual involvement, said Rita Katz, executive director of the SITE Intelligence Group. Katz said that Amaq’s claim suggested that Artan did not coordinate with the group, but that it had spent time looking at news reports to determine his motivation.

The bloodshed in Columbus on Monday occurred after the Islamic State issued instructions this month about carrying out attacks using knives and vehicles, Katz said. And as long as these instructions are online, similar attacks are likely to continue, she said.

On Tuesday, the Amaq News Agency, which is linked to the Islamic State, also said that the attack was carried out in response to the group’s “calls to target citizens,” the same language used when the group claimed credit for the Minnesota mall stabbings in September.

After the deadly attacks in Paris last year, detailed news releases with video recordings and photos were quickly sent out. It took two days for Amaq to claim credit for the attack in San Bernardino, Calif., last year, saying that “supporters of the Islamic State” had carried out the mass killing. In September, it took a day for Amaq to claim that the attacker who stabbed 10 people in a Minnesota mall was a “soldier” of the group.

Authorities have not established a motive in the attack. But the law enforcement investigation increasingly is focusing on the possibility that Artan was motivated by radical or terrorist influences, though he had no actual contacts with the Islamic State or other overseas terror groups, a U.S. official said.

FBI investigators are working jointly with local authorities and are keenly interested in a Facebook post – believed to be from Artan – that talks of abuses against Muslims and the radical cleric Anwar al-Awlaki. FBI spokesmen declined to comment on the Islamic State’s claim that Artan was a “soldier” of the group. An FBI spokesman said Artan was unknown to the bureau before Monday.

A U.S. official said Artan came to the U.S. from Somalia as a refugee in 2014, and stayed at least for a time in the Dallas area before moving to Columbus. He was a community college student in Columbus from 2014 to 2016 and transferred as a junior to Ohio State this semester.

FBI Director James B. Comey has warned Congress about the screening of refugees, saying in 2015 of those coming from Syria: “I can’t sit here and offer anybody an absolute assurance that there’s no risk associated with this.”

On Wednesday morning, president-elect Donald Trump said the attack came at the hands of “a Somali refugee who should not have been in our country.”

Social media groups in favor of the Islamic State had celebrated the attack on Monday after reports emerged about Artan’s possible Facebook post ranting about the treatment of Muslims, but that reaction had ebbed by a day after the violence, Katz said.

According to CNN, the Facebook post apparently written shortly before the attack says that if Muhammad were alive today he would be labeled a terrorist by the Western media and that “seeing my fellow Muslims being tortured, raped and killed in Burma led to a boiling point. I can’t take it anymore.”

In the aftermath of the attack — which authorities said appeared to have been planned — classes resumed at Ohio State on Tuesday morning with sorrow, fear, numbness, and a call for unity.

Artan, an Ohio State student whose neighbors in Columbus said was Somali, was shot to death by a university public safety officer within minutes of his outburst, which injured 11 people.

The attack Monday morning, as classes were beginning after the Thanksgiving break, sent crowds of students sprinting to safety while others barricaded themselves in classrooms not knowing what was happening. Three victims of the attack remained hospitalized Tuesday afternoon, according to the chief medical officer at the Wexner Medical Center, Dr. Andrew Thomas: “We expect all of the individuals to make a full recovery.”

A professor hurt in the attack spoke at a news conference Tuesday afternoon shortly after being discharged from the hospital, where he was treated for severe lacerations that he said left bloody footprints all down a hallway where he fled. William Clark, an emeritus professor of materials science and engineering, was hit by the car driven by Artan, thrown into the air and landed on concrete.

“It happened so fast,” he said. “It seemed to me literally within 15 to 30 seconds I heard the shots and it was over.”

Clark said he was withholding judgment about Artan’s motives and the claim that he was a “soldier” of the militant Islamic State.

“Anybody can take responsibility for anything if they see it as a feather in their cap,” Clark said, adding that as a research professor he wanted to know more facts about the case, such as whether there were personal family issues or social issues involved. “Before I pass judgment on this young man, I would like to see exactly what the circumstances are and exactly why he took the course of action.”

He also said he was mindful of this: Artan is dead. And, Clark said, “I’m going home this afternoon.”

Law-enforcement officials said they are investigating the origins of Artan’s apparent social-media rant about the treatment of Muslims. Artan also recently told the student newspaper the Lantern that he was scared to pray in public on the Ohio State campus. Some presumed that those frustrations might have served as motivation for the attack.

Artan appeared to be “radicalized online by jihadist propaganda,” Rep. Adam B. Schiff (Calif.), ranking Democrat on the House Intelligence Committem said in a statement Tuesday.

“We still have not seen evidence that he was directed or in communication with any overseas terror organizations, nor do we know the totality of the circumstances that led his family to the United States, or whether his time abroad influenced his decision to launch an attack on the campus yesterday,” Schiff said.

Schiff said the attack highlighted the dangers presented by “lone wolves and others who have been self-radicalized or recruited online” as well as the nearly impossible task of trying to stop every possible plot.

“In some cases, and Abdul Razak Ali Artan may be one of them, there may be little or no outward indication that anything is amiss or that the person has changed,” he said. “That is what makes these situations so difficult to prevent; once set in motion, they are almost impossible to stop completely.”

A day earlier, Schiff had said the attack bore the hallmarks of something carried out by “carried out by someone who may have been self-radicalized.”

That sentiment, which emerged almost immediately after police publicly identified Artan, led to concern from some in the Columbus Somali and Muslim communities that people angered or frightened by the attack might target them for retribution. Some at Ohio State described students and faculty as bracing for the day Tuesday, facing the unknown.

At a time when the country is already deeply divided over issues of immigration, with President-elect Donald Trump having vowed to prevent Islamist extremists from entering the country, the attack was particularly searing.

The university had a message prominently on their home page Tuesday morning: “Together we remain unified in the face of adversity. Today and always, we’re all Buckeyes.”

Community members planned to gather in the evening to promote unity and healing.

While police say Artan was alone during the attack, authorities have not ruled out the possibility that he might have had some form of help, Columbus police chief Kim Jacobs said Tuesday.

“Everybody has a lot of people in their life, and we need to talk to people that knew him and find out what they knew about him,” Jacobs told WOSU public radio. “Were there any signs? Were there any people that he worked with, cooperated with, were perhaps influenced by?”

Investigators seeking a motive for the attack are going to sift through Artan’s online postings as well as what he has said to people who knew him, Jacobs said. She said authorities are looking at a Facebook posting believed to be from Artan to see if it provides insight into what may have prompted the attack.

“I believe that it discusses his feelings about the current status of his faith and some of his troubles,” Jacobs said. “Certainly, that will be looked at, kind of gone over, pored over, to determine whether or not there was a basis there for his actions.”

Columbus has the second-largest Somali community in the country, according to Abukar Arman, a local Somali community leader who also served as Somali special envoy to the United States from 2000 to 2013. Somalis make up the largest immigrant group in the city.

Most of the Somalis arrived in the late 1990s, after fleeing civil war and strife in their home country. Some had initially settled elsewhere in the U.S., but came to Columbus for work, he said.

Horshed Noah, executive director of the Abubakar Assidiq Islamic Center mosque in Columbus near Artan’s home, said that the violence stunned members of the Somali refugee community. “In times like this you have to stand up and explain the true image of Islam,” Noah said. “We must fight against stereotypes. We all share this planet.”

Some student groups posted statements on social media.

The act of violence that occurred at The Ohio State University earlier today was frightening and shocking. Such hatred...

Posted by Somali Students' Association at The Ohio State University on Monday, November 28, 2016

On Facebook, there was an outpouring of support for the Somali Students’ Association at Ohio State after the group posted a statement condemning Monday’s violent attack and offering prayers for the victims.

“We know that some will connect this tragedy with the ethnicity or religion of the attacker,” the group said. “Neither our Somali heritage nor our faith condones the harming of innocent people.”

That prompted responses such as, “You don’t need to defend your humanity. You are welcome here.”

“Blessings to you guys,” another wrote. “Columbus wouldn’t be the Columbus I love without you and the richness you bring to it.”

Arman said the group, which has 500 to 600 members, also has been bombarded with hate mail in the past 24 hours.

“Here is where my fear is,” he said. “This will play into further stigmatizing of American Muslims, and those of Somali Muslims in particular because it plays right into the narrative of the president-elect.”

There was a very clear anti-Somali, anti-Muslim current in many digital forums at Ohio State, said Pranav Jani, a professor in the English department who is not Muslim but serves as an adviser to several student organizations with Muslim members. He mentioned examples such as a Muslim student leader being told the group was complicit with ISIS and another student being asked to name a single example of a Christian or a Jewish person carrying out a violent attack. Jani also said that when someone wrote in comments on a student newspaper’s website that there was no evidence that the attack was motivated by Artan’s religion, another person responded: “What evidence do you need? 9/11, London, Paris, San Bernadino, Nice, Brussells, Boston, and hundreds of others? Denial is not a solution”.

Echoing President Drake's statement tonight - We are Buckeyes. We love our campus and we love what Ohio State stands...

Posted by Muslim Students' Association at The Ohio State University on Monday, November 28, 2016

On Tuesday morning, the Muslim Students’ Association at Columbus State Community College responded to questions with a collective statement:

“I write this to you from a place of deep sadness and utter shock after the tragic events that took place yesterday. The tragic incident that happened in OSU. . . . Our police departments will continue to be on alert at all Columbus State locations. The safety of students, faculty members, staff, and visitors is of the highest importance.
“Our thoughts and prayers are with those who have been hurt and those whose families have been torn by this tragic incident, also with the first responders who fearlessly went in to shield the danger away from escalating.
“Our prayers are also with the countless lives that will be affected by this tragedy in the future.”

Ohio State, like many across the country, has had tensions during a polarizing campaign and after the election.

Fliers advising white women not to date black men, and other white-supremacist ideas, were posted on campus earlier this month, as they were at several other colleges.

OSU student Tony Buss, director of diversity and inclusion for the Undergraduate Student Government, said he’s heard that Muslims on campus have been verbally harassed. He said his Muslim friends have expressed concern about hate speech in the past year, including some incidents in the past month.

The president of the student government association, and members of the Buckeyes for Trump student group did not immediately respond to requests for comment Tuesday.

Jani said that after the election, hundreds of students reached out to campus leaders with concerns about how they, as immigrants, or minorities, would be treated during a Trump administration. The attack yesterday intensifies all that emotion.

“The whole OSU community just coming to campus today is a bit nervous — whatever their background,” he said. “This was terrorizing for everybody.”

Nick Anderson and Ellen Nakashima contributed to this report from Washington. Shapiro reported from Columbus; Svrluga, Hauslohner, Berman and Zapotosky reported from Washington.

Correction: An earlier version of this report gave an incorrect title for Tony Buss. The story has been updated.