Investigators have found evidence that the man who plowed a car into a crowd at Ohio State University Monday before stabbing several pedestrians with a butcher knife was inspired by ISIS propaganda, law enforcement sources told Fox News.
The sources did not specify what evidence was found, but investigators are inclined to believe that the attacker, 18-year-old Abdul Razak Ali Artan, was "self-radicalized."
Artan also praised American-born Al Qaeda cleric Anwar al-Awlaki as a “hero” and railed against U.S. interference in Muslim lands in a series of Facebook posts, officials said.
"America! Stop interfering with other countries, especially the Muslim Ummah. We are not weak. We are not weak, remember that," Artan wrote on Facebook, using the Arabic term for the world's Muslim community.
The posts from Artan's account came to light after Monday's violence, which left 11 people injured before Artan was shot and killed by a university police officer.
"Every single Muslim who disapproves of my actions is a sleeper cell, waiting for a signal. I am warning you Oh America!" Artan also said.
The posts were recounted by a law enforcement official who was briefed on the investigation but wasn't authorized to discuss it publicly and spoke on condition of anonymity.
Al-Awlaki, who was a senior Al Qaeda leader, was killed more than five years ago during a CIA-led U.S. drone strike. Before his death, al-Awlaki was involved in several terror plots in the United States, using his fluent English skills to draw recruits to carry out attacks.
The FBI is now in possession of Artan’s electronic devices and will focus their investigation on whether he was reading the two recent ISIS propaganda journals that called for attacks using vehicles and knives, a law enforcement source added.
In recent months, federal law enforcement officials have raised concerns about online extremist propaganda that encourages knife and car attacks, which are easier to pull off than bombings.
ISIS has urged sympathizers online to carry out lone-wolf attacks in their home countries with whatever weapons are available to them.
On Tuesday, ISIS's media arm claimed the Ohio State University attacker was a "soldier of the Islamic State." According to MEMRI, the terror organization's A'maq News Agency said Artan "carried out the operation in response to calls to target citizens of the countries [participating] in the international coalition."
"Brother Abdul Razak Ali Artan, God accept him, implementer of the Ohio attack, a student in his third year in university," the post read.
According to law enforcement sources, Artan was born in Somalia and was a legal U.S. permanent resident.
Sources told Fox News that Artan attended Columbus State Community College and graduated with an associate’s degree earlier this year. Allen Kraus, the school’s vice president of marketing and communications, said the former student had no record of behavioral or disciplinary issues during his time at CSCC.
Ohio State's student newspaper, The Lantern, ran an interview in August with a student named Abdul Razak Artan, who identified himself as a Muslim and a third-year logistics management student who had just transferred from Columbus State in the fall.
He said he was looking for a place to pray openly and worried about how he would be received.
"I was kind of scared with everything going on in the media. I'm a Muslim, it's not what media portrays me to be," he told the newspaper. "If people look at me, a Muslim praying, I don't know what they're going to think, what's going to happen. But I don't blame them. It's the media that put that picture in their heads."
Officer Alan Horujko, 28, who stopped Artan from hurting more people, is being hailed a hero. Ohio State University Police Chief Craig Stone said Horujko, who joined the force in January 2015, was near where Artan attacked because of a gas leak and arrived on the scene and shot the knife-wielding Artan in less than a minute.
Surveillance photos showed Artan in the car by himself just before the attack, but investigators are looking into whether anyone else was involved, the campus police chief said.
Classes at OSU were canceled after the attack, but resumed on Tuesday. The school planned a vigil for Tuesday night at its basketball arena.
Three of the 11 victims remained hospitalized Tuesday evening, but all were expected to recover.
Students said they were nervous about returning and planned to take precautions such as not walking alone.
"It's kind of nerve-wracking going back to class right after it," said Kaitlin Conner, 18, of Cleveland, who said she had a midterm exam to take Tuesday.
Leaders of Muslim organizations and mosques in the Columbus area condemned the attacks while cautioning people against jumping to conclusions or blaming a religion or an ethnicity.
Fox News reporters Catherine Herridge, Garrett Tenney and Matt Dean contributed to this report. The Associated Press also contributed to this report.