The photo was taken directly after Yamaguchi stabbed Asanuma and is seen here attempting a second stab though he is restrained before that happens. Otoya Yamaguchi was member of a right-wing ultranationalist Japanese group. Inejiro Asanuma was leader of the socialist party in Japan. He was unusual in postwar Japan for his forceful advocacy of socialism, and his support of the Chinese Communist Party was particularly controversial. Asanuma was assassinated during a televised political debate for the coming elections for the House of Representatives. While Asanuma spoke from the lectern at Tokyo’s Hibiya Hall, Yamaguchi rushed onstage and ran his wakizashi through Asanuma’s abdomen, killing him.
Otoya Yamaguchi was a member of a group which, among other things, wished to rid Japan of Western influence and restore Japan’s traditional culture. He chose a weapon that was fitting his purpose, and that meant getting up close and attacking with complete conviction, knowing full well that there was no way he would be getting away.
Less than three weeks after the assassination, while being held in a juvenile detention facility, Yamaguchi mixed a small amount of tooth paste with water and wrote on his cell wall: “Seven lives for my country. Long live His Imperial Majesty, the Emperor!” Yamaguchi then knotted strips of his bedsheet into a makeshift rope and used it to hang himself from a light fixture. The phrase “seven lives for my country” was a reference to the last words of 14th century samurai Kusunoki Masashige.
Footage of the incident was captured live by a Japanese television company. The picture was taken at about 0:27 in the slow-motion video. You can even see the flash of the camera and the pose the assassin strikes in the photograph as everyone rushes toward him. He got pushed or dragged, so even though he enters from the right, in this picture of the second stab attempt he is on the left a few seconds later. Here’s a helpful diagram.
(Photo taken by Yasushi Nagao and with this photo he won the 1961 Pulitzer Prize and the 1960 World Press Photo of the Year award.)