UCF police said Wenliang Sun had altered his appearance and his behaviour was changing.
US authorities are set to deport a Chinese college student who made no threats but alarmed a roommate and a friend with his distressing behaviour and had bought two semiautomatic rifles, the media reported.
Police at the University of Central Florida (UCF) said they were first alerted by a campus official in late January that Wenliang Sun, 26, was a "student of concern", CNN reported late Saturday.
Sun had altered his appearance and his behaviour was changing, UCF police Chief Richard Beary said.
The police contacted the Bureau of Alcohol, Tobacco, Firearms and Explosives and were told Sun owned an AR-15-style rifle and ammunition.
"We know that in today's world that a person in distress who owns a high-powered firearm, we just cannot ignore that," Beary said. "We have a duty and an obligation to make sure our people are safe."
There was "red flag after red flag", that something bad would happen, he added.
The red flags, according to Beary, included Sun being uncommunicative with others and not leaving his room, dying his hair blond, paying for a fast expensive car with cash, and referring to one of his guns as a "sniper rifle", CNN reported.
"I think there was a disaster about to happen and we stopped it," the chief said.
Sun's non-immigrant student status was revoked when federal authorities learned he that was not attedning class.
As an international student, he was required to do so in order to maintain his visa.
On March 21 a federal judge ruled he should be sent home. Sun is not allowed to return to the US for 10 years.
Sun is currently at a US Immigration and Customs Enforcement holding facility in Macclenny, Florida.
The date for his deportation was not immediately known.