Investigative sources say that the suspect in the shooting death of former Japanese Prime Minister Abe Shinzo told them that he made up his mind to kill Abe one year ago.

Yamagami Tetsuya is being held on suspicion of shooting the former prime minister while he was giving a campaign speech in the city of Nara on Friday.

The 41-year-old suspect has told investigators that his motive was a grudge against a religious organization. He said he believed Abe had close ties with the group.

The sources also say that Yamagami said he had initially plotted to use explosives, but eventually opted to use a firearm. He explained that this was because his only intended target was Abe.

Police have confiscated other handmade guns from his home. They also found out that Yamagami may have test-fired guns in mountainous areas.