EL PASO, Texas (AP) — The alleged ringleader of a gang of escaped Texas convicts on the run for the past three weeks is portrayed by authorities as fearless and possessed of remarkable criminal ingenuity.

Above all, they say, he is cold-blooded.

"I have little doubt that if somebody had gotten on the wrong side of George Rivas, they'd have had a bullet hole in them," Dr. Richard E. Coons, a forensic psychiatrist who examined Rivas' file in 1994, said this week.

The seven convicts broke out from the state prison at Kenedy on Dec. 13 by stealing clothing from staff members and bluffing their way to the rear gate. They seized a cache of guns and left a note warning, "You haven't heard the last of us yet."

Since then, the group, believed to be hiding out in the Dallas-Fort Worth area, is accused of pulling off a Christmas Eve holdup at a sporting goods store in Irving in which a police officer was slain with extraordinary viciousness. Aubrey Hawkins was shot 11 times — six times in the head — and was also run over by a vehicle.

The robbers, dressed as security guards, escaped with $70,000 in cash and checks, guns and police scanners.

On Thursday, FBI agents filed federal charges of unlawful flight to avoid federal prosecution for capital murder, broadening the manhunt.

"This enables federal law enforcement to conduct an investigation nationally and internationally if warranted," spokeswoman Lori Bailey said.

The gang is made up of two killers, two armed robbers, a child abuser, a serial rapist and a burglar. The FBI has drawn up psychological profiles of them, and investigators believe Rivas, 30, is the gang's leader. Rivas was serving a life sentence for robbery and kidnapping.

The gang's methods in the Irving robbery are similar to those in at least two other holdups allegedly masterminded by Rivas in El Paso in 1993. In those two cases, Rivas used deception, disguises, two-way radios and the threat of deadly force — an M.O. that an appeals court once said was "like a signature" on Rivas' part.

During one of the holdups, Rivas persuaded a clerk at a sporting goods store to let him stay in the building after closing time by saying a friend had to go home to get money so Rivas could buy ski boots.

Then he pulled a gun and forced the clerk to use the store intercom to call other employees to the basement.

He handcuffed all of the employees but one to a ski-grinding machine. He then toured the store with the remaining employee, taking $5,905 in cash and 58 guns. As he toured the store, he didn't touch anything, forcing the employee to do the work.

Rivas warned the employees that he had written down their license plates and could find out where they lived. And he warned that he would be watching the phones and would come back and kill them if anyone called police.

After about 20 minutes, when there were no more sounds from upstairs, the employees dragged the heavy ski grinding machine to a phone and called police. Then they moved the machine back in case Rivas returned.

Rivas got caught in the other El Paso holdup, at a Toys 'R' Us. Cornered in the building by police, he didn't give up easily. Rivas climbed into an air-conditioning duct and then tried to hide on the roof.

In his 1994 report, Coons wrote: "He demonstrates an unusual degree of interest, creativity and intensity in his craft. He is a mastermind and a leader. He is confident and arrogant. He has no conscience and does not speak the truth."

Rivas' crimes include at least a dozen robberies and other offenses in Texas, Arizona and New Mexico.

Coons said Rivas' history doesn't contain the overt physical abuse or other trouble that can shed light on a criminal personality. His parents divorced when he was 6 and his mother remarried. Rivas lived with his father and his grandmother.

Forensic psychiatrist Dr. Karen Gold, who worked with Larry Harper, another of the escaped convicts, said she believes Harper is a pliable henchman for Rivas. Harper, 37, was serving 50 years for sexual assault.

Harper "suffered physical and emotional abuse at his mother's hands. He's much more likely to be compliant," Gold said. "I see him as so desperate for approval and acceptance that if he fell in with bad company, to stay in their good graces, he'd do whatever he had to."

Gold said Rivas "was always one scary dude. Abusive, violent and vain. Obsessed with guns."