Officers say they were called to a home in Richmond after reports of a disturbance.
There they say they found Dwayne Wallick, 37, 'straddled' over 90-year-old Ruby Wallick.
Dwayne Wallick is now facing a charge of murder after his gran was pronounced dead at the scene.
A police spokesman said officers were called to the home shortly after 2pm local time to reports of suspicious circumstances.
Ruby is said to have been 'missing pieces of flesh' and paramedics were called.
An autopsy is pending into the cause of death. It is unclear if she was killed before officers say they found her grandson eating her.
Wallick is said to been taken to hospital for a medical examination and has not been booked into jail.
A spokesman said Wallick was 'in the process in committing those injuries' when he was found.
Police tasered the suspect and were forced to restrain him.
