A researcher for a defense company jumped from an apartment building on Monday in an apparent suicide, prosecutors said, amid an investigation over his alleged involvement in shady defense equipment dealing.

The 43-year-old Kim, who was working for LIG Nex1, was found by his wife at 2:45 a.m. in the apartment complex where he lived in Osan, Gyeonggi Province, 55 kilometers south of Seoul, prosecutors said.

Before he was found, Kim left a text message to his wife saying he got involved in a probe over his mistakes and that he is sorry, police said.

The Seoul Central District Prosecutor's Office said Kim had been summoned twice as a suspect in August and was to be questioned for the last time on Monday.

LIG Nex1 is suspected of providing defective equipment used to assess the performance of anti-tank guided missiles to the Agency for Defense Development between 2012 and 2014, which cost more than 8 billion won ($6.7 million) in total.

The agency is suspected of overlooking faulty parts.

"Kim was questioned with a lawyer accompanying him in both summons and there were no problems in the process of questioning," prosecutors said.

On Aug. 25, prosecutors raided the offices of LIG Nex1 and the ADD as a part of the prosecution's investigation into corruption in the defense industry.

A special investigation team -- comprised of government, military and prosecution officials -- has cracked down on corruption in the industry after a series of questionable deals came to light over the past year. (Yonhap)