Police investigating the stabbing rampage on Awaji Island in Hyogo Prefecture said Tuesday the family of one of the victims had sought police help nine times in February and March.
The police on Monday arrested Tatsuhiko Hirano, a 40-year-old unemployed man, for allegedly stabbing five of his neighbors to death in Sumoto, the island's main city.
On Tuesday the charges against him were changed from attempted murder to murder and the police sent his case to the public prosecutor's office.