Prosecutors said Gale William Nettles, 66, was arrested with a pickup truck containing 1,500 pounds of fertilizer that he allegedly thought was volatile ammonium nitrate, the same farm fertilizer used to blow up the Oklahoma City federal building.
Nettles, previously convicted of counterfeiting, had been released from prison in 2003, had lived in Chicago and apparently had a grudge against the court system, said U.S. Attorney Patrick J. Fitzgerald.
Fitzgerald said Nettles was not working with any other groups but had asked cooperating witnesses about contacting Al Qaeda and Hamas.
CBS Chicago affiliate WBBM-TV reports Nettles was arrested at a park early Thursday with the pickup truck when he met undercover agents who he thought were terrorists willing to buy a fertilizer bomb for $10,000 to destroy the Dirksen federal building, according to the criminal complaint.
"He had a rational plan to build a bomb. We weren't going to wait to see if it would work," Fitzgerald said.
Authorities said Nettles targeted the Dirksen federal building in downtown Chicago, which houses federal criminal and civil courts and the U.S. attorney's office.
Nettles had been living out of a transient hotel. Two police officers guarded the front door of the rooming house Thursday afternoon and refused to let reporters through, saying a search was being conducted.
According to the complaint, Nettles met July 26 with an undercover agent he thought was a member of a terrorist group. In a recorded meeting, Nettles said he had a half ton of ammonium nitrate in New Orleans that he could have in the city in two days and that he had a target in mind -- the U.S. courthouse downtown, the complaint said.
Nettles told the undercover agent he could make a 3,000-pound fertilizer bomb. Timothy McVeigh had used 4,800 pounds ammonium nitrate to blow up the Oklahoma City federal building in 1995, killing 168 people.
Ammonium nitrate is one of the most common farm fertilizers in the world, and instructions for turning it into a bomb are available on the Internet. A truck bomb of ammonium nitrate and fuel oil destroyed the Oklahoma City federal building in 1995, killing 168. There are other fertilizers that do not have as much explosive potential.