Mr Shindo, who lived with his parents, had initially told police that he did not notice anything unusual at home during the time of the attack, agency Kyodo News reported.
Investigators seized several knives from the family’s home and were trying to identify the murder weapon, Jiji Press reported.
They have not given out a motive for the murder.
Bears were initially presumed to be to blame for Fujiyoshi Shindo’s death because Japan has seen a rising number of bear attacks in recent years. In the 12 months to March 2024, a record 219 people were attacked by bears – and six of them died, Japan’s Environment Ministry said.
In July, a newspaper deliveryman was killed by a brown bear in a residential area.
The rise in bear encounters have also prompted authorities to relax hunting laws to make it easier for people to shoot bears.
Thousands of bears have recently been trapped and killed by hunters.