A senior official from South Korea's anti-corruption body, who had spearheaded high-profile and politically sensitive investigations involving first lady Kim Keon Hee and former opposition leader Lee Jae-myung, was found dead Thursday.

The official was found deceased in his apartment in Sejong City with a suicide note at around 9:50 a.m. Thursday by a person who visited the apartment after the official failed to show up to work or answer calls.

Police are looking into the exact circumstances of the death.

According to the state-run Anti-Corruption and Civil Rights Commission, the official had served as the acting director of the ACRC’s anti-corruption bureau and was responsible for overseeing various integrity policies and investigations until recently.

The official handled politically sensitive cases, including opposition leader Lee Jae-myung's use of a helicopter after he came under a knife attack in January.

The official had been involved in examining allegations against first lady Kim Keon Hee, who was accused of improperly receiving a Christian Dior luxury handbag worth 3 million won ($2,178).

In June, the ACRC closed the "luxury handbag scandal" case after its panel reviewed whether the receipt of the luxury bag was relevant to President Yoon Suk Yeol's official duties or whether the bag should be classified as presidential records.

The state anti-corruption agency determined that there were no violations of the anti-graft act, as there was no punishment clause for public officials' spouses.

This review and the subsequent decision, however, placed significant pressure on the official.

According to JTBC, the official disclosed in a recent phone call with a friend that senior ACRC officials had pressured him to close the case despite his reservations, stating, "I felt immense psychological pressure."

On Tuesday, the official sent a Kakao Talk message to an acquaintance saying, "I am feeling psychologically overwhelmed, I am sorry to have disappointed recently. It's truly difficult," according to local reports.

Last month, the official also appeared at a parliamentary hearing to answer questions from lawmakers.