CINCINNATI - U.S. officials have arrested an Ohio man in connection with a plan to attack the U.S. Capitol building in Washington, CBS News has confirmed.

Christopher Lee Cornell, 20, is pictured in a Jan. 14, 2015, booking photo provided by the Butler County Jail after his arrest in connection with a plot to attack the U.S. Capitol. Butler County Jail

Christopher Lee Cornell -- also known as Raheel Mahrus Ubaydah -- was arrested by the FBI for the attempted killing of a U.S. government officer and for possession of a firearm in furtherance of attempted crime of violence, according to the criminal complaint against him, filed in the U.S. District Court in Cincinnati.

The apparently ISIS-inspired plot, which included guns and bombs, was stopped very early in its formation. In the wake of last week's terror attacks in Paris against satirical newspaper Charlie Hebdo and a kosher grocery store, the U.S. has reaffirmed its commitment to preventing individuals from being radicalized by extremist groups like ISIS.

From the summer of 2014 through this month, Cornell, 20, established and used Twitter accounts under the alias Raheel Mahrus Ubaydah. He posted videos, statements and other content expressing support for the Islamic State of Syria and Iraq (ISIS), according to the criminal complaint.

FBI agents arrest Christopher Lee Cornell at the Point Blank Range and Gun Shop on Jan. 14, 2015, in Cincinnati, Ohio. WKRC

On Aug. 29, 2014, Cornell allegedly told an FBI informant via an instant messaging platform that he wanted to commit violent jihad. He told the informant, "I believe we should meet up and make our own group in alliance with the Islamic State here and plan operations ourselves."

Get Breaking News Delivered to Your Inbox

Cornell and the informant met in Cincinnati in October and again in November, the court document says. In their second meeting, Cornell allegedly revealed that he considers members of Congress enemies and wanted to attack the Capitol.

Cornell allegedly wanted to build, plant and detonate pipe bombs near the Capitol building and then use firearms to kill officials and employees at the Capitol. Cornell shared with the informant the research he had conducted to carry out the plan, the criminal complaint says.

Then, around Tuesday or Wednesday, Cornell and the informant took the final steps to travel to Washington.

Cornell was arrested Wednesday morning by the the FBI's Cincinnati-Dayton Joint Terrorism Task Force at the Point Blank Range and Gun Shop in Colerain Township, Ohio, just purchasing two semi-automatic rifles and around 600 rounds of ammunition. The gun store cooperated with investigators, according to manager John Deen.

"We've known for about a week that something was going to happen, but we didn't know when it might happen," Deen told CBS affiliate WKRC in Cincinnati. "When an agent showed up this morning was the first inkling that we had that something was going to happen today. From our perspective we were just cooperating with federal and local law enforcement to be able to facilitate whatever operation they had going on. So from our perspective it was, for the most part, kind of a matter-of-fact firearms sale."

Deen said the suspect did not indicate what he planned to do with the weapons, aside from using the shooting range at a future time. He described Cornell as "maybe a little shy, a little bashful but talkative. No, no -- If I hadn't been warned ahead of time, there wasn't really anything about him that would have suggested that he was involved in something like this."

WKRC spoke with John Cornell, the suspect's father, who described his son as a "mama's boy" who was close to his family and lived with his parents. He said Cornell spent a lot of time alone and on his computer -- which was among the items FBI investigators removed from the family's home.

"I don't think he really knew where he wanted to go in life," John Cornell said Wednesday night, adding that his son had converted to Islam within the last six to eight months.

"We never talked too much about his faith until, like, the last couple of weeks he finally started opening up," he said.

The father told WKRC Cornell had a seasonal job but not a lot of money, and that he didn't know where his son got the funds to purchase firearms and ammunition. Cornell had no previous experience with guns, according to his father, who alleged his son was "definitely set up."

"I know how they operate," John Cornell said. "I don't care if people like what I have to say. I know how they operate. They will set you up."

CBS News spoke with a former classmate who went to Oak Hills High School in Cincinnati with Cornell and his older brother, John Cornell II. The classmate and John were in the same class, a year ahead of Christopher.

"Chris was always an odd individual that I personally stayed away from," said the classmate, who described him as "a weird kid in school."

"Chris seemed to be the normal one, more so than his brother," the classmate told CBS News. "John was always a little off. Both were very quiet. No one really was friendly with them or invited them to hang out. They were kind of loners."