The father of one of the men described him as a stay-at-home "Mommy's boy," while the other young man's attorney said he was "a normal 23-year-old kid."

Neither had a history of violent crime, but the two Ohio men are now charged separately with plotting to kill fellow Americans in support of Islamic extremists.

The terrorism cases in the nation's heartland underscore the difficulties in detecting potential homegrown terrorists and illustrate the different paths they may take toward radicalization.

Christopher Lee Cornell, 21, of suburban Cincinnati, was arrested Jan. 14 on charges he planned to attack the U.S. Capitol with pipe bombs and shoot officials and employees as they fled. In the other, Abdirahman Sheik Mohamud, 23, of Columbus, was arrested in February and subsequently indicted on charges he planned to attack a military base or prison after returning from terrorist training Syria. Both have pleaded not guilty.

Mohamud, a U.S. citizen born in Somalia, was part the large Somali community in Columbus that U.S. Senator Rob Portman, R-Ohio, said during a recent Senate hearing on homeland security is "very concerned" about radicalization efforts. The government's allegations say Mohamud had shown support for a brother who died in Syria, fighting for a terrorist group.

Cornell, meanwhile, had worked little since high school, lived with his parents, and spent a lot of time on the Internet, which U.S. authorities say is increasingly a source of extremist propaganda and recruiting.

Portman called the arrests a case study of "two very different challenges."

There are, however, some similarities: authorities said social media postings played into both men's cases, with Mohamud making pro-militant Facebook postings and Cornell interacting on Twitter under his adopted Muslim name with a man who turned out to be an FBI informant.

Individuals bent on terror — so-called "lone wolves" — or small groups are tough to uncover, said Mark Ensalaco, the director of human rights research at the University of Dayton who has also written about Middle East terrorism and the Sept. 11 attacks.

"It's a nightmare for national security," he said. "The fewer people in a conspiracy, the easier it is to conceal."

He said detection can come from confidential informants and government electronic surveillance, but that can raise concerns about protecting citizens' rights.

Cornell's father John has said he was misled and coerced by "a snitch." The FBI said an informant seeking favorable legal treatment in an unrelated criminal case made contact with Cornell — going by his adopted Muslim name of Raheel Mahrus Ubaydah — last August on Twitter and the two used social media to communicate.

Cornell claimed he was in contact with people overseas and said that while he didn't think he would get specific authorization for a U.S. attack, he believed they should "wage jihad" in support of the Islamic State, the FBI said in an affidavit. Events following that Aug. 29 message led to Cornell's arrest after he bought two M-15 assault weapons and 600 rounds of ammunition, according to federal court documents.

Mohamud appeared determined to follow in the footsteps of his brother, who authorities say died last year fighting for a terrorist group in Syria. He sent his brother Facebook messages of support in 2013 and 2014 and later bought a tablet computer to use to raise money for his brother's fighting, according to the government.

The FBI "was first made aware of" his brother's Facebook page in September 2013, the agency said in a court filing without providing details of that discovery.

Mohamud also offered signs of growing radicalism on social media, with images of the Islamic State flag and pro-militant postings, authorities said. His indictment refers to two unnamed associates that he gave information to, although it's not clear whether they were informants.

While Cornell grew a beard and long hair and adopted Muslim religious practices, his parents said he seemed to be at peace. However, local police said he disrupted a Sept. 11 memorial ceremony in 2013 while holding up a sign saying "9-11 was an inside job." In a March jail interview with WXIX-TV of Cincinnati, Cornell said he had wanted to go to Washington and shoot President Barack Obama in the head for "American aggression" against the Islamic State.

Ensalaco said for family and close friends, recognizing potential violent radicalism can be comparable to recognizing someone is becoming suicidal — changes in behavior, "signs they are troubled." But, he added: "It's very hard."

Michael McCaul, chairman of the House Homeland Security Committee, has said federal authorities are aware of "thousands" of potential U.S. extremists. And although it's unclear what connections, if any, Cornell had to other extremists, he predicted to WXIX-TV there are more attacks coming.

"We are pretty strong," Cornell said. "We're in every single state you can name, just about."

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AP Legal Affairs Writer Andrew Welsh-Huggins in Columbus contributed to this report.

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Contact Dan Sewell at http://www.twitter.com/dansewell