In Japan, the death penalty is done by hanging. Prisoners are only notified about an hour beforehand, and family members find out after the fact. So Rika Matsumoto knew that any day, her father might be gone. Her father was Shoko Asahara, the leader of Aum Shinrikyo, a Japanese doomsday cult. On March 20, 1995, Aum members spread sarin gas in the Tokyo subway system during morning rush hour. 17 people died, and thousands more fell ill. Asahara was arrested, along with several other cult members. Rika was 12 years old. Asahara was executed on Friday, 23 years after the attacks. A few years ago, Matsumoto had begun to publicly campaign for a retrial for her father, saying that he had been mentally unfit to stand trial. But even now that her father is dead, some people are still asking questions about what happened. To see more about how Japan is still dealing with the deadliest attack on Japanese soil since WWII, watch the video above. Subscribe to VICE News here: http://bit.ly/Subscribe-to-VICE-News Check out VICE News for more: http://vicenews.com/ Follow VICE News here: Facebook: https://www.facebook.com/vicenews Twitter: https://twitter.com/vicenews Tumblr: http://vicenews.tumblr.com/ Instagram: http://instagram.com/vicenews More videos from the VICE network: https://www.fb.com/vicevideo