On November 5, 1989, Tsutsumi Sakamoto (坂本 堤, Sakamoto Tsutsumi; April 6, 1956 – November 5, 1989), a lawyer working on a class action lawsuit against Aum Shinrikyo, a doomsday cult in Japan, was murdered, along with his wife Satoko and his son Tatsuhiko, by perpetrators who broke into his apartment. Six years later, following the 1995 attack on the Tokyo subway, the murderers were uncovered and it was established that the murderers had been members of Aum Shinrikyo at the time of the crime.
Source: “Tomomasa Nakagawa”, English Wikipedia (CC BY-SA 4.0), excerpt