The FBI on Wednesday arrested an Ohio man for allegedly plotting an attack against the Capitol that was inspired by the Islamic State in Iraq and Syria (ISIS).

Christopher Lee Cornell, a 20-year-old man from the Cincinnati area, is facing charges of attempting to kill U.S. officials and possession of a firearm to commit an act of violence, according to a complaint filed by federal prosecutors in a U.S. district court in Ohio.

Cornell allegedly told an FBI informant he wanted to detonate homemade pipe bombs at the Capitol building and then fire on officials and their staff, calling members of Congress the “enemies.”

The FBI stressed in a statement that the “public was not in danger during this investigation."

"I applaud the FBI and other law enforcement officials on their work to thwart this potential terrorist act," Sen. Rob PortmanRob PortmanHillary gives Bernie cool reception at Trump inaugural lunch GOP governors defend Medicaid expansion Senators introduce dueling miners bills MORE (R-Ohio) said in a statement Wednesday evening. "It is an important reminder of the very real threat that radical Islam continues to pose to the homeland."

"Once again, our dedicated law enforcement officials — state, local, and federal — have taken swift and appropriate action to keep our nation safe and secure," said fellow Ohio Sen. Sherrod BrownSherrod BrownMajor progressive group unveils first 2018 Senate endorsements Congressional leaders unite to protect consumers Mnuchin weathers stormy confirmation hearing MORE (D) in a statement. "We must ensure that they continue to have the resources they need to safely and effectively perform their jobs.”

House Homeland Security Chairman Michael McCaul said the "threat should set off alarm bells" about "violent Islamist extremism."

Cornell used Twitter accounts since September under the alias Raheel Mahrus Ubaydah, where he posted statements, videos and other content "indicating his support" for ISIS, the FBI said in an affidavit included in a criminal complaint against Cornell. 

A confidential informant tipped off the FBI last fall in order to soften the punishment in his own, unrelated criminal case, according to government documents. The informant and Cornell connected on Twitter in August 2014, then began exchanging messages on another platform thereafter.

In one instant message in August, Cornell said he had been in contact with people overseas and said he didn't think he could get authorized to carry out a terrorist attack in the U.S. but wanted to anyway, according to the complaint.

“I believe that we should just wage jihad under our own orders and plan attacks and everything,” Cornell told the informant in an instant message, the FBI's affidavit said.

“I believe we should meet up and make our own group in alliance with the Islamic State here and plan operations ourselves," he said.

On Wednesday, Cornell allegedly purchased a pair of M-15 semi-automatic rifles and 600 rounds of ammunition ahead of a planned trip to Washington, D.C. Agents arrested him soon after.

Before buying the weapons, Cornell targeted specific government buildings, researched how to make pipe bombs and scouted out a store to buy Smith & Wesson semi-automatic rifles, officials said.

The FBI said Cornell initially aimed to travel to Washington with the informant in order to scout multiple government buildings and had jihadi videos about constructing bombs on his computer.

Cornell "also voiced support for violent jihad" and discussed his support for ISIS with the FBI informant during an October meeting in Cincinnati, according to the court document.

FBI Special Agent T.A. Staderman said in the complaint that the agency had "probable cause" to believe Cornell attempted to kill government officials and posses a firearm for attempted violence.

The arrest comes less than a day after news emerged that authorities had arrested another Ohio man for an alleged plot to poison Speaker John BoehnerJohn BoehnerLast Congress far from ‘do-nothing’ Top aide: Obama worried about impeachment for Syria actions An anti-government ideologue like Mulvaney shouldn't run OMB MORE (R-Ohio) at a country club.

"Once again, the entire Congress owes a debt of gratitude to the FBI and all those who keep us safe," Michael Steel, a spokesman for BoehnerJohn BoehnerLast Congress far from ‘do-nothing’ Top aide: Obama worried about impeachment for Syria actions An anti-government ideologue like Mulvaney shouldn't run OMB MORE, said in a statement to The Hill.

— This story was updated at 7:32 p.m.