Dozens of federal agents and local police work side by side pursuing people they believe have ties to terrorism in the Chicago area. They say they are finding a new threat is emerging as they continue their fight against terrorism.
In the last 18 months, 34 Americans from around the country have been charged with having ties to terrorism. Analysts call it an unprecedented spike.
ABC7 talked to the man whose job it is to intercept those intent on terrorism before they can commit an act.
"The thing that scares me the most is the lone wolf. The one guy we do not know about," said Bob Holley, FBI Chicago, Counter-Terrorism.
The people that worry those in the business of counter-terrorism the most can be found sitting at a computer; those in this country, rejected by others, dejected about the American way of life and susceptible to recruitment via the internet.
"We call 'em lone wolves. That individual who is not on our radar that is not connected to any of the known individuals we may be looking at but he's inspired by al-Qaeda or any of these other terror groups," said Holley.
Holley is the assistant special agent in charge of the FBI's Counter-Terrorism Unit in Chicago. He oversees six squads of investigators that include FBI agents and Chicago Police.
It was on Holley's watch that David Coleman Headley popped on the FBI's radar. Headley is a Pakistani-born US Citizen who was living in Chicago in 2009. He pleaded guilty to casing targets for hotel bombings in India that killed 160.
Holley says Headley proved to be a treasure trove of information.
"I think it's self-preservation and I think that's the way it was with Headley. Headley thought, 'If I cooperate, I'll get some cooperative points further down the road.' " Did his cooperation save lives? "Absolutely, no doubt."
The FBI is reluctant to talk about terrorism's tentacles in the Chicago area - specifically how deep sympathies may run.
Last spring, agents plucked Raja Khan out of a cab he was driving in the Loop and charged him with sending money to a group with ties to al-Qaeda and talking of bombing a sports stadium in the US.
Khan's lawyer said his client was simply supporting a group that opposes Indian control of Kashmir.
"I don't see al-Qaeda as freedom fighters, so if you're providing material support - whether it be money or some type of expertise you may have - if you're providing that, you're a terrorist," said Holley.
He says many of the FBI's victories don't get announced as press conferences.
"What you see most of are the indictments, the prosecutions. What you don't see is the intelligence we gather here in Chicago," said Holley.
This is Bob Holley's last week in Chicago. He's been promoted to run a unit at the FBI's secretive counter-terrorism headquarters outside of Washington. There, it'll be his job to oversee all of the terrorism cases that originate in the United States looking for connections between suspected cells in different U.S. cities and overseas.