TROY — Peiching Dong, a Rensselaer Polytechnic Institute student from Shanghai, took an Uber from Troy to a gun shop in Saratoga County on March 14 intending to buy a rifle.

He left the store in the custody of two FBI agents.

Now expelled from RPI, he’s sitting in a federal detention center in Batavia, waiting for a hearing on his immigration status. Regardless of its outcome, Dong doesn’t plan to return to Troy in the immediate future and is hoping to simply go home to China.

“He’s been through a lot,” said Dong’s Latham-based lawyer, Mark Sacco.

The RPI campus has been rattled by the circumstances surrounding the detention of the 19-year-old freshman, who was studying chemistry and physics. On Monday — nearly two weeks after the initial incident — the school issued a statement announcing that Dong had been permanently removed.

“It’s definitely the thing on campus right now,” said one student, speaking on condition of anonymity.

Dong’s odyssey started when he was driven to the Saratoga Weapons and Tactical gun shop in Malta.

He was interested in buying a high-end rifle, but the fact that he offered his passport and student visa as identification raised a potential concern for Rob Porter, who owns the store. He called federal authorities to inquire if it was all right to sell a firearm to Dong.

“We made some calls to some departments that have asked us in the past to ‘See something, Say Something,’" Porter said.

State Police said they didn’t think there was a problem with the purchase. The FBI, however, wanted to talk to Dong.

So the student canceled his Uber ride back to Troy and waited about a half-hour for agents to arrive.

Porter said there was nothing about Dong’s demeanor or behavior that raised any red flags. “He seemed like a nice kid,” he said. Dong did, however, show him his switchblade knife — which Porter informed him was illegal in New York.

Nor was his interest in firearms unusual. Tom King, who heads the New York State Rifle and Pistol Association, said Chinese people who have traveled to the U.S. often have an interest in guns, which are far more difficult to legally own back home.

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Sacco said the FBI agents took Dong to an RPI dean’s office where he was immediately expelled. While the school hasn’t offered a detailed explanation as to why, RPI has a policy against weapons on campus. Dong's dorm room was searched by federal authorities after his expulsion and detention.

Sarah Ruane, spokesman for the FBI’s Albany office, stressed that no criminal charges were involved in the case.

Even so, the consequences were severe: With Dong expelled, his visa was no longer valid. He was taken to the Rensselaer County jail, where agents from the federal Immigration and Customs Enforcement picked him up and took him across the state to the Batavia detention center.

The arrest sent shock waves across the normally placid RPI campus, sparking a social media eruption full of speculation and worry.

On Monday, the school sought to tamp down potential rumors, issuing a statement that said the school had been "informed by federal law enforcement that a student was attempting to purchase an assault rifle."

"With the intervention of law enforcement, and our own Public Safety division, the purchase was prevented," the statement continued. "The student was permanently removed from the university and remains in federal custody.”

The statement added that, “At no time were guns or ammunition on the Rensselaer campus, nor was there any immediate threat to the campus community.”

The reference to an assault rifle was an apparent error: The sale of assault-style weapons has been banned in New York for years, with the definition of what constitutes such a weapon expanded by the 2013 SAFE Act gun control law.

It’s not unusual for students in the U.S. to leave or be deported if their F-1 visa expires or is voided, said L.J. D’Arrigo, an Albany immigration lawyer.

But that’s usually because a student has flunked out, isn’t taking enough credits or has simply stopped attending classes. And unlike other kinds of visas, federal ICE agents get immediate notice of an expiration from the sponsoring college or university.

“A student visa is different because it is much more regulated,” said D’Arrigo.

Additionally, the fact that he was taken to Rensselaer County Jail likely sealed Dong’s fate: The county’s sheriff, Pat Russo, has a policy of detaining undocumented immigrants and calling ICE agents to check on them.

Sacco said Dong’s father has flown from China to New York, and they are working to get him out of detention as soon as possible. They also plan to appeal his expulsion from RPI, although that process could take a while. And it’s unclear whether he wants to return to the school.

“This is Dumb Kid 101,” Sacco said, characterizing Dong’s attempted gun purchase as an honest mistake.

“It was terrible circumstances coming together,” said Sacco. “Things looked more suspicious than they were, and you have a climate in this country — justifiably so — of all these gun issues.”

Mallory Moench contributed to this story.

rkarlin@timesunion.com 518 454 5758 @RickKarlinTU