CINCINNATI — A 20-year-old Ohio man’s Twitter posts sympathizing with Islamic terrorists led to an undercover FBI operation and the man’s arrest on charges that he plotted to blow up the U.S. Capitol and kill government officials.

Christopher Lee Cornell, also known as Raheel Mahrus Ubaydah, told an FBI informant they should “wage jihad,” and showed his plans for bombing the Capitol and shooting people, according to a criminal complaint filed in federal court in Ohio Wednesday. The FBI said Cornell expressed his support for the Islamic State.

Cornell’s arrest came only days after a grand jury indictment charged another Cincinnati-area resident with threatening to murder House Speaker John Boehner.

Boehner spokesman Michael Steel said in a statement Wednesday: “Once again, the entire Congress owes a debt of gratitude to the FBI and all those who keep us safe.”

The complaint against Cornell charges him with attempting to kill officers and employees of the United States.

Cornell was arrested Wednesday after buying two semi-automatic rifles and about 600 rounds of ammunition, authorities said.

The public was never in danger, said John Barrios, acting special agent in charge of the FBI’s Cincinnati division.

A phone message and an e-mail were left Wednesday for attorney Karen Savir, a federal public defender listed in court records as Cornell’s attorney. A working phone number could not be found for Cornell’s family.

His father, John Cornell, told The Cincinnati Enquirer in a story for Thursday’s editions that his son was a “momma’s boy who never left the house.” He said his son endured frequent incidents of abuse as a practicing Muslim.

“Everything you’re hearing in the media right now, they’ve already painted him as some kind of terrorist,” John Cornell told the newspaper. ... “They’ve painted him as some kind of jihadist. ... (Christopher) is one of the most peace-loving people I know.”