Robert Hanssen, a former FBI agent turned spy whom the bureau describes as the most damaging in its history, was found dead in his prison cell, United States authorities have said.

Hanssen, who became an FBI officer on 12 January 1976, used the alias “Ramon Garcia” when corresponding with his handlers.

Also Read: Anna Shay Family: Father, Edward Shay, mother Ai-San, Brother, Allen Shay, son Kenny Kemp

According to the FBI’s website, he “compromised numerous human sources, counterintelligence techniques, investigations, dozens of classified US government documents, and technical operations of extraordinary importance and value”.

While there was some suspicion around his unusual activities occasionally, he was not caught for years.

Also Read: Was Anna Shay married? Bling Empire star’s personal life was shrouded in mystery

After the spy Aldrich Hazen Ames was arrested by the FBI in 1994, the bureau realized classified information was still being leaked, which is what instigated the investigation into Hanssen.

He had been due to retire so the FBI acted quickly in an effort to catch him “red handed”. To lure him back to FBI headquarters for closer monitoring, he was given a fake assignment.

Also Read: 5 Facts to know about Anna Shay, Bling Empire star, after her death at 62

Hanssen began working in his new office – complete with hidden cameras and microphones – at FBI headquarters in January 2001. A month later, investigators learned he was scheduled to make a dead drop at a park.

 On 18 February 2001, Hanssen went to Foxstone Park, located in Virginia, with a plastic bag filled with classified materials.

The FBI had seen him frequent the park before and as he returned to his vehicle, he was arrested and taken into custody. During his arrest, he asked FBI agents, “What took you so long?” He told interrogators that the FBI security was pathetic, but he cooperated to avoid the death penalty.

He pleaded guilty to 15 counts of espionage and in May 2002 was sentenced to life without parole.