A manhunt is under way in Texas after a death row inmate walked out of a Houston jail in civilian clothes and with a fake badge.
Thompson was sentenced to death less than a week ago
Charles Victor Thompson, 35, apparently changed out of his usual orange overalls in a room used for discussions between inmates and lawyers.
Thompson was convicted of murder after shooting his ex-girlfriend and her boyfriend dead in 1998.
However he was sentenced to death only last Friday.
"He still has not been found," said Lieutenant John Martin, sheriff of Harris County, about seven hours after the escape from Baker Street jail.
Thompson was being held in a high-security unit, although the prison was a county jail, as Thompson had still not been moved to a higher-category jail.
Authorities described him as 5ft 11in (180cm) and weighing about 16st (104kg), and say he was wearing a dark blue shirt, khaki trousers and white sports shoes.
"He managed to get some civilian clothing. He had changed out of the orange jumpsuit that inmates ordinarily wear," Lt Martin told the Houston Chronicle.
"We don't know exactly where he got that from."
Authorities said they were searching central Houston and the surrounding area, concentrating on likely escape routes.
An investigation was under way into how he got the clothes and a law enforcement identity card.
"It definitely suggests that this was pre-planned and strongly suggests he had help in making his escape," Lt Martin said.
The sheriff told the Chronicle that about 3,300 prisoners were held in the Baker Street jail.
Thompson's escape was the first since the facility was built about three years ago, he said.
The relatives of Thompson's victims, Dennise Hayslip, 39, and Darren Keith Cain, 30, were shocked at the news.
"This is something that's just unfathomable to me," said Ms Hayslip's brother, Mike Donaghy, 45.
"How can a convicted murderer get away like that? How did he get in civilian clothes? How did he get a badge?"