PALO PINTO, Texas -- Authorities were investigating late Tuesday night after a well-known inmate suddenly died while in custody at the Palo Pinto County Jail.

James Richard Little, 73, suffered a "major medical episode" shortly after eating dinner, according to Sheriff Brett McGuire.

"We have the Texas Rangers investigating," he told WFAA by phone. "We tried to do CPR. He was unresponsive."

Little was in custody on aggravated assault with a deadly weapons charges after an alleged knife attack last week.

But the man is best known for being involved in a series of high-profile bank robberies in the 1980s, where helicopters were used as part of the heists.

As the Mineral Wells Index first reported this week, Little's adventures and convictions with the law came after a decorated stint as a lawman himself with the Alaska State Troopers.

Before that, he served admirably in Vietnam, according to a 1989 book about the man's tragic life entitled "Once a Hero," by Howard Swindle.

McGuire said Little was suffering from mental illness while at the jail, and that they were trying to find him proper medication.

Mineral Wells police say there was a standoff with him last week after he stabbed a motel clerk while threatening the clerk's mother.

No one at that time knew of his notorious past.

"Just goes to show you don't ever know who you're interacting with in our profession," Chief Dean Sullivan said on Tuesday.

The clerk, who didn't want to reveal his name, showed WFAA cuts and stab wounds to his fingers and abdomen.

He said they were shocked by what happened, and even more surprised when they learned of Little's history.

"We had to fight him off and lock ourselves in the office before the cops came," he said. "Sounds like he had this history, using helicopters to make his escapes. Guess he has a pretty colorful past."

The Texas Rangers are expected to investigate the jail death.