Japan marked the 24th anniversary Wednesday of a deadly sarin nerve gas attack on Tokyo’s subway system carried out by the Aum Shinrikyo cult, which killed 13 people and injured more than 6,000 others.

In a memorial ceremony at Kasumigaseki Station, relatives of the victims and employees of the subway operator observed a moment of silence at 8 a.m., around the time when the attack occurred on March 20, 1995.

The doomsday cult’s founder, Shoko Asahara, and several of his former followers were executed for the crime last July.

“After the executions, I came here with a different feeling than before,” said Shizue Takahashi, who lost her husband, Kasumigaseki assistant stationmaster Kazumasa Takahashi, in the attack. “Half a year has passed and I am thinking about the consequences of capital punishment more deeply.”

Following prolonged trials, Asahara, 63, whose real name was Chizuo Matsumoto, was convicted of numerous murders, including the 1995 sarin gas attack, and hanged along with 12 other former senior members of the cult.

Immediately after the executions, Takahashi, 72, said her suffering had not stopped and that she was having a “very hard time.” But on Wednesday, she said she has started to think about how the executed death row inmates had spent their time in prison and how their families are doing.

Stands for flowers were set up by Tokyo Metro Co. at Kasumigaseki and other stations where people fell victim to the attack. Kasumigasaki Station is in a district containing many ministerial and other governmental offices.

The nerve agent was scattered in five subway cars during the morning rush hour under Asahara’s instructions, causing mayhem at the stations.

With the Tokyo 2020 Olympics and Paralympics approaching, the government is considering ways to further strengthen the safety of the country’s railway system.

The Land, Infrastructure, Transport and Tourism Ministry conducted an experiment at Kasumigaseki Station earlier in the month to check whether a body scanner can detect hazardous materials if a passenger tries to secretly carry them onto trains.

The ministry hopes the device will enhance safety without affecting the convenience of railway passengers.