(BanditTracker Chicago)

He wore a dreadlocks wig, covered his face, and plotted his escape. But the one thing a bank robber in suburban Chicago didn't account for, according to police, was getting stuck in an air duct.

Charles Estell, 38, was charged with one count of bank robbery in federal court Sunday.

Investigators said Estell held them on an 11-hour stand-off at the Bank of America branch at a strip mall in Oak Lawn, with a restaurant and other stores nearby.

According to a criminal complaint released by the F.B.I. Chicago office, Estell staked out the bank and somehow learned there was an opening in the building's roof that led to the bank vault.

Two female bank employees were in the vault at around 2:15 p.m. Saturday, getting ready to close for the day, when a man suddenly walked into the vault.

The robber was wearing a ski cap, had a bandana covering his face, and a dreadlocks wig.  He was holding a gun in his hand, and according to the complaint, told the employees, "This is a robbery, get down on the floor, keep your heads down. I don't want to kill or hurt you, I just want the money."

The robber then tied the employees' hands with black zip-ties, and duct-taped their mouths and feet, telling the employees, "I have someone outside, I don't want to shoot you, give me 10 minutes."

After he shoved about $100,000 into a backpack and a duffle bag, the FBI says surveillance video captured the robber pacing back and forth inside the bank branch.

Witnesses in nearby businesses spotted the robber through the bank's windows, and told ABC station WLS-TV in Chicago that the robber appeared to be talking on a cell phone.

"He was crawling on his hands and knees like a dog. He had a cell phone in one hand and a pistol in the other hand," witness Conrad Rusin said.

Bank security guards saw the robbery on closed circuit surveillance cameras as it was happening inside the vault and called police, who arrived almost immediately.

Oak Lawn police say the robber tried to walk out the front door, but ran back in to the bank, when he noticed police were already on the scene.

The robber then decided to make his exit through the building's air duct system, which is linked to neighboring businesses and office buildings in the strip mall.

More than 60 SWAT members and other officers arrived on the scene and spent nearly 11 hours searching for and trying to communicate with the bank robber, whom they suspected still had to be somewhere inside the strip mall.

Just before 1 a.m. Sunday, a broken window and a trail of blood led authorities to an air duct in a neighboring office building. Police found Estell stuck inside the duct, unable to free himself.

"He was wedged in there. He did not communicate. We had to physically cut him out of the vent to get him out," Oak Lawn Police Division Chief Michael Kaufman told ABC News.

Investigators are still trying to figure out how he learned about the vault's location.

"There's no doubt he had some knowledge," Kaufman said. "He definitely had a plan, but apparently his plan failed. "

Police recovered the cash and the loaded handgun used in the robbery, stashed near the roof of the building, he said.

"He tried to hide the money and gun, hoping, it seemed, to locate it a later time, if he had escaped," Kaufman said.

According to Illinois Department of Corrections records, Estell was out on parole after serving time on vehicular hijacking charges.

Oak Lawn Police said the two female bank employees were shaken up, but not injured.