Police helicopters and canine units swarmed the area, but not until more than three hours after Joseph "Jose" Banks and Kenneth Conley went unaccounted for during a 5 a.m. headcount, U.S. Marshal's Service spokeswoman Belkis Cantor said.
Both men were still at large late Tuesday night.
Investigators found a broken window in the men's cell, where window bars were found inside a mattress, according to an FBI affidavit filed late Tuesday. Fake metal bars also were found in the men's cell, a rope was tied to a window bar, and each man's bed was stuffed with clothing and sheets to resemble a body, the affidavit said.
It appeared to illustrate a meticulously planned escape from the 27-story facility that came a week after Banks made a courtroom vow of retribution. Both men are facing hefty prison sentences, and the FBI said they should be considered armed and dangerous.
SWAT teams stormed at least one home in Tinley Park, a suburb south of the city. Although neither man was found, evidence suggested that both had been at the home just hours earlier, according to the FBI.
Some schools went on lockdown after being inundated with calls from nervous parents. Mike Byrne, a superintendent in Tinley Park, said "our parents are so emotionally charged right now" because of the school shootings in Connecticut.
Hours after the escape, a rope possibly made of bed sheets could be seen dangling down the side of the Metropolitan Correctional Center. At least 200 feet long and knotted about every 6 feet, the rope was hanging from a window that was 6 feet tall but only 6 inches in diameter.
The facility is one of the only skyscraper lockups in the world, and experts say its triangular shape was meant to make it easier to guard, theoretically reducing blind spots for guards. The only other escape from the nearly 40-year-old facility occurred in the mid-1980s, Cantor said.
Exactly when Banks, 37, and Conley, 38, escaped remains unclear. Shop owners across the street from the wall the men scaled said police suddenly flooded into the area around 8:30 a.m., hours after they missed a headcount. Police initially said the men escaped sometime between 5 a.m. and 8:45 a.m.
Both men were wearing orange jumpsuits, but police believe they may have quickly changed into white T-shirts, gray sweat pants and white gym shoes. The FBI believes both men were in Tinley Park, a heavily wooded area about 25 miles south of Chicago. Authorities were scouring a local forest preserve in the afternoon.
Banks, known as the Second-Hand Bandit because he wore used clothes during his heists, was convicted last week of robbing two banks and attempting to rob two others. Authorities say he stole almost $600,000, and most of that still is missing.
During trial, he had to be restrained because he threatened to walk out of the courtroom. He acted as his own attorney and verbally sparred with the prosecutor, at times arguing that that U.S. law didn't apply to him because he was a sovereign citizen of a group that was above state and federal law.
After he was convicted by U.S. District Judge Rebecca Pallmeyer, he said he would "be seeking retribution as well as damages," the Chicago Sun-Times and Chicago Tribune reported.
When the judge asked how long he needed to submit a filing, Banks replied: "No motion will be filed, but you'll hear from me."
Pallmeyer, a prominent federal judge who oversaw the corruption trial of now imprisoned former Illinois Gov. George Ryan, appeared to stick to her regular schedule Tuesday and there were no signs of extra security. Her office declined comment.
Conley pleaded guilty last October to robbing a Homewood Bank last year of nearly $4,000. Conley, who worked at the time at a suburban strip club, wore a coat and tie when he robbed the bank, and had a gun stuffed in his waistband.
Both men were being held in the Chicago lockup, which houses around 700 inmates awaiting trial in the Dirksen Federal Building a few blocks away. It is one of the only skyscraper jails in the world, said Jennifer Lucente of Chicago Architecture Foundation.
Architect Harry Weese designed the building in the mid-1970s shortly after notorious prison riots in Attica, N.Y., and was asked to design a "more humane" lockup, Lucente said. That was one reason Weese ensured each cell had a window, she said.
The brother of Hollywood director Christopher Nolan also tried to escape in 2010. Matthew Nolan, who was being held pending an extradition request, was sentenced to 14 months in jail for plotting to escape from by hiding a rope made out of bed sheets in his cell.
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