On May 10, 2002, singer Ashanti’s debut single “Foolish” continued its run at the top of the Billboard Chart of Pop Singles.

She may as well have been singing about convicted spy Robert Hanssen, who was sentenced to life in prison without the possibility of parole that same day.

Hanssen, 73, received $1.4 million in cash and diamonds in exchange for classified information he gave the Soviet Union and Russia over a 20-year period. Some of the documents he gave to the Russians were marked “Top Secret” and “codeword,” and included “technical operations of extraordinary importance and value,” the FBI said in a press release at the time.

The FBI began watching Hanssen in 2000 after they identified him from a fingerprint and from a tape recording supplied by a disgruntled Russian intelligence operative, according to CNN.

Authorities arrested him on Feb. 18, 2001 after he dropped off classified documents in a Virginia park. He later was charged with 21 counts of spying for the Soviet Union and Russia, and eventually was convicted of espionage and conspiracy. Hanssen had worked for the FBI for 25 years at the time of his arrest.

Then FBI Director Louis J. Freeh had this to say at the time of Hanssen’s arrest:

“A betrayal of trust by an FBI Agent, who is not only sworn to enforce the law but specifically to help protect our nation’s security, is particularly abhorrent. This kind of criminal conduct represents the most traitorous action imaginable against a country governed by the Rule of Law. It also strikes at the heart of everything the FBI represents — the commitment of over 28,000 honest and dedicated men and women in the FBI who work diligently to earn the trust and confidence of the American people every day.”

When it was all said and done, FBI officials found that Hanssen had forked over more than 6,000 pages of valuable material, according to the affidavit.

It didn’t have to be this way. Hanssen’s wife Bernadette caught him with classified documents in 1981 and pleaded with him to stop spying, according to CNN. He did – for four years. But he resumed his illegal activity in 1985.

The depth of the damage Hanssen caused continued to be discovered as late as 2015, when U.S. officials became concerned that he may have compromised a top-secret tunnel project, according to the Associated Press. The U.S. built the tunnel under the Russian embassy in Washington D.C. so the government could spy on Russian personnel working there.

These high profile cases are the types of stories that people often think of when they think of someone having their security clearance revoked, says Catie Young, who specializes in security clearance law.

“Thankfully, they are few and far between,” Young says. “But they are a stark reminder of the importance of upholding your oath to protect the sensitive information you come into contact with when you hold a security clearance.”