I believe the assassin used a homemade or 3D printed shotgun.
“Shinzo Abe, Japan’s longest-serving prime minister, died at the age of 67 Friday after being shot during a campaign speech in western Japan. It was a shocking attack in a country that has some of the strictest gun control laws in the world.
Abe was shot from behind minutes after he started his speech Friday in the city of Nara. He collapsed bleeding and was airlifted to a nearby hospital in Nara, although he was not breathing and his heart had stopped, the Associated Press reported. He was later pronounced dead after receiving massive blood transfusions, officials said. …”