HOUSTON -- Deputies fear trial witnesses in the case of a man convicted of killing his ex-girlfriend and another man who escaped from a downtown Houston jail could become victims of retaliation, KPRC-TV in Houston reported.

Officials with the Texas Department of Criminal Justice informed the murder victims' relatives and witnesses shortly after authorities said Charles Thompson, 35, walked out of Harris County Jail's Baker Street facility at about 3:30 p.m. Thursday.

"This is 100 percent human error. It's not like he defeated a locking mechanism or broke a hole in a wall. He convinced people to essentially let him out," Harris County Sheriff's Department Lt. John Martin said.

Authorities said Thompson, who was convicted of killing his ex-girlfriend and her boyfriend, used a fake badge and a change of clothes to disguise himself as an attorney to elude workers and escape from the jail.

"Apparently these were the clothes he used during his last court appearance, and what we've found is that he either put his jumpsuit over his clothing or put the clothes in with his legal papers when he came back to the jail," Martin said.

KPRC reported that the fake badge Thompson showed jail workers had his picture on it.

"At no time did (officials) actually have it in their hands where they could really closely scrutinize this badge," Martin said. "It was a laminated card, like a driver's license or something of that nature."

During the investigation, Thompson was caught trying to hire a hit man to kill a prosecutorial witness in his murder trial, which is why authorities believe he could target witnesses again.

"My understanding is they were notified very early yesterday when this happened by TDCJ personnel so they are well aware of it and extremely concerned. The fear is that he could seek retaliation against them," Martin said.

Thompson calls himself the "Chuckster Killer" and has planned two murder-for-hire plots for trial witnesses from his jail cell. Authorities believe he could act on those plots because he has nothing to lose.

"He has been twice sentenced to death, and he has absolutely no incentive to cooperate with law enforcement," Martin said.

Thompson kicked in the door of Dennise Hayslip's north Harris County apartment in April 1998. Her boyfriend at the time, Darren Cain, was also inside the apartment when Thompson opened fire on them. They were pronounced dead at the scene.

The Texas Court of Criminal Appeals upheld Thompson's convictions last Friday and was sentenced to death a second time for the murders of Hayslip and Cain.

Officials said that he was transferred from death row to the Harris County Jail on Thursday for a court appearance. While there, he persuaded guards to let him out of his cell for an attorney visit. Authorities believe that was one of two ruses he used to escape the jail.

"He also had some kind of a tag or ID that suggested he was with the Attorney General's Office. He approached the floor control center and the deputy saw his tag. It apparently was convincing enough that the deputy allowed him to leave the building," Martin said.

Authorities said they are not sure if Thompson had help in his escape, but said it was well planned and executed.

Every law enforcement agency in the area is on the lookout for Thompson. Authorities consider Thompson extremely dangerous and say he should not be approached if spotted.

Thompson is a white man, 5 feet 10 inches tall and weighs about 180 pounds. He was last seen wearing khaki pants, a dark blue shirt and white tennis shoes before escaping the jail.

Anyone with information is asked to contact the Harris County Sheriff's Office at (713) 221-6000, the Criminal Warrants Division at (713) 755-6055 or 911.