Aldrich Ames, a longtime Central Intelligence Agency (CIA) case officer who betrayed U.S. intelligence by spying for the Soviet Union and later Russia, died at the age of 84.

The Bureau of Prisons website shows that Ames died on Monday. 

He was being held at the Federal Correctional Institution in Cumberland, Maryland, where he was serving out a life sentence.

The FBI said it arrested Ames, a 31-year veteran of the CIA, in 1994 on espionage charges, after he began passing classified information to the KGB in 1985, compromising numerous CIA and FBI human sources, some of whom were later executed.

RUSSIA UPS JAIL SENTENCE OF US CITIZEN TO 10 YEARS FOR BEATING PRISON STAFF

The agency said Ames, a Russian-speaking CIA officer who specialized in Russian intelligence services, secretly provided classified materials to the KGB using "dead drops," which are concealed locations where documents were left to be retrieved later by Soviet intelligence officers operating out of the USSR Embassy in Washington.

AMERICAN WITH ‘CIA’ CREDENTIALS AND VARIETY OF WEAPONS ARRESTED IN MEXICO

Ames ultimately pleaded guilty to espionage charges in 1994 and was sentenced to life in prison without the possibility of parole, in one of the most damaging spy cases in U.S. history.

"Well, the reasons that I did what I did in April of 1985, were personal, banal, and amounted really to kind of greed and folly. As simple as that," Ames said in an interview archived by the National Security Archive at George Washington University.

"I knew quite well, when I gave the names of our agents in the Soviet Union, that I was exposing them to the full machinery of counterespionage and the law, and then prosecution, and capital punishment, certainly, in the case of KGB and GRU officers who would be tried in a military court, and certainly others, that they were almost all at least potentially liable to capital punishment," he added. "There's simply no question about this."

Wes Street, the director of the National Counterintelligence and Security Center, said on X in 2022 that Ames volunteered to work for the KGB and compromised over 100 Soviet and East European cases and multiple U.S. assets.

"Ames received payments from the KGB that totaled $2.5 million, making him one of the highest paid American spies," Street wrote. "The KGB kept another $2.1 million earmarked for him in a Moscow bank."