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The most alarming thing about a string of recently arrested terror suspects is that they are all Americans. WASHINGTON (AP) — One was a drywall contractor and father, another a petite woman who cared for the elderly, another a U.S. military officer. The most alarming thing about a string of recently arrested terror suspects is that they are all Americans.

Over the past week, a Pennsylvania woman was accused in a plot to kill a Swedish cartoonist; a New Jersey man was held by authorities in Yemen; and five young Pakistani-American men from Northern Virginia were charged by Pakistani officials with planning terrorist attacks in the South Asian country. These seven are among more than a dozen Americans captured or identified by the U.S. government and its allies as actively supporting jihad, or holy war, in the past two years.

Some, according to prosecutors, were inspired by the U.S. involvement in the Iraq and Afghanistan wars. Others, like the accused Pennsylvania woman, allegedly wanted to avenge what they considered an insult to the Prophet Mohammed. Many traveled overseas to get terrorist training. Some used home computers to foment plots.

There is no evidence that these cases are connected in any way. But they underscore the new reality that there is a threat from violent Islamic extremism from within the U.S. It is difficult to say whether the uptick in cases is because law enforcement has gotten better at catching suspects or if there are simply more to catch.

Most of the cases ended with suspects captured before they could act on their plans. But some were nearly ready to spring to action, like Colorado resident Najibullah Zazi, 24, who pleaded guilty in February as the leader of a plot to bomb the New York subway system.

And law enforcement was too late to prevent a shooting rampage in November on the military post at Fort Hood, Texas. Army Maj. Nidal Hasan, 39, a U.S.-born Army psychiatrist of Palestinian descent, is charged with killing 13 people.

Determining how quickly a suspected homegrown terrorist goes from adopting extremist rhetoric to becoming a suicide bomber is a challenge to law enforcement. Some people never make that leap. Others do it in a matter of months or years.

"Individuals can be radicalized in a number of ways — by direct contact with terrorists abroad or in the United States, over the Internet or on their own through a process of self-radicalization," said Assistant Attorney General David Kris, the top counterterrorism official at the Justice Department.

These cases, Kris said, "underscore the constantly evolving nature of the threat we face."

For years U.S. officials have predicted there would be a rise in homegrown terrorism. "Now we're beginning to see the predictions coming true," said Michael Chertoff, the former Homeland Security secretary.

Because of this, Chertoff said, it is critical for communities to be on the lookout for unusual behavior. Law enforcement, he added, needs to continue to educate people on the differing signs of terrorism.

There is no single reason people drift toward terrorism.

"It's a combination of psychology, sociology and people who, just for cultural reasons, gravitate" to Islamic extremism, Chertoff said. "We can't assume we've got months and years."

ColleenLaRose, the Pennsylvania woman who allegedly met violent jihadists online under the name "JihadJane," took only months, prosecutors say. LaRose, according to her boyfriend, never showed religious leanings during the five years they dated. Then, her boyfriend came home last summer and she was gone.

In a June 2008 YouTube video, the blond-haired, green-eyed Muslim convert said she was "desperate to do something somehow to help" ease the suffering of Muslims, federal prosecutors allege.

Some homegrown terrorists take much longer to show their militant leanings. In the case of North Carolina drywall contractor Daniel Boyd, federal prosecutors say he nursed his ambitions for jihad over decades.

Boyd is accused of leading a group of men — including two of his sons — who planned to kidnap, kill and maim people in other countries in the name of jihad. One of Boyd's neighbors said he didn't think Boyd was a terrorist. "If he's a terrorist, he's the nicest terrorist I ever met in my life," Charles Casale said.

Boyd decried the U.S. military, praised the honor in martyrdom, bemoaned the struggle of Muslims and said "I love jihad" on audiotapes obtained by federal authorities.

Even when law enforcement officials know about an American's interaction with suspected terrorists, they may not have enough information to act on it.

Months before Hasan allegedly went on his shooting spree at Fort Hood, he was in contact with a radical Islamic cleric in Yemen, federal prosecutors allege. The FBI was aware of Hasan's contact with the cleric, but he did not emerge as a homegrown threat before the shootings.

It is not a new concept for Americans to join the jihadi cause. In 2001, John Walker Lindh was arrested in Afghanistan for fighting with the Taliban. Raised Catholic, the California native was 12 when he saw the movie "Malcolm X" and became interested in Islam. A few years later, the teenager who liked hip-hop music converted to Islam.

There are disaffected, alienated people everywhere in the United States who, for decades, have joined gangs and cults in search of an identity. Radical Islamist groups are yet another destination for those who seek purpose in their lives, experts say.

Jihadi groups that recruit and inspire are nebulous and in many cases small and connected only by extremist ideology espoused on the Internet. The appeal is the notion that "somebody does want me," said Jack Tomarchio, a former top intelligence official at the Homeland Security Department.

Being an American with terrorist leanings is not an automatic ticket into a group like al-Qaida. Many of these groups are suspicious of Americans and worry they are spies for the U.S. government.

But in the world of jihadi recruitment, it's like winning a gold medal when an American is trusted and decides to join a terrorist network, Tomarchio said.

In many cases they have no criminal record and can blend into society, like the woman who allegedly called herself Jihad Jane, and travel internationally with ease.

"I know there are more of them out there," Tomarchio said.

The spate of cases over the past two years shows the conventional wisdom about who is a terrorist is dangerously outdated, said Bruce Hoffman, a terrorism expert at Georgetown University.

"There really is no profile of a terror suspect; the profile is broken," said Hoffman. "It's women as well as men, it's lifelong Muslims as well as converts, it's college students as well as jailbirds."

CIA director Leon Panetta said, in an interview with The Washington Post, that there is concern about the increasing number of terrorism suspects who have no criminal record. Zazi and Umar Farouk Abdulmutallab, the Nigerian charged with attempting to detonate explosives aboard a commercial flight about to land in Detroit on Christmas, were among those Panetta cited.

"How many other Zazis are there? The people who have a clean record who suddenly for some crazy reason decide to get involved with jihad," said Panetta. "The bomber in Detroit. This person suddenly goes off, has a U.S. visa, and within 30 days he's recruited to strap a bomb on and come to this country. What we are seeing is that they are now looking for those kind of clean credentials."