The 18-year-old nephew intercepted his aunt when she was on her way to grind rice in a nearby place yesterday afternoon and attacked her with a sharp weapon injuring her fatally, sub-divisional police officer of Chakradharpur Subodh Kumar Jaiswal said.
The woman's husband and daughter, who rushed to her rescue, were also injured.
On being informed, a police team rushed to the village and arrested the man.