A 74-year-old North Carolina man has pleaded guilty to murdering his wife of 53 years - and says he did so to prevent her living as a 'caged animal' in a nursing home.

Frank Mansfield admitted to shooting dead his wife Phyllis Mansfield, 73, in the garage of their Elizabeth City home in the December 2016.

He was in the process of looking for an assisted living center for his wife who suffered from dementia and Alzheimer's disease when he realized death was the better option.

Frank Mansfield, 74, pleaded guilty Wednesday to killing his wife of 53 years Phyllis Mansfield, 73, in their North Carolina home in December 2016

Frank called police the morning of December 14, 2016 and reported he had shot his wife.

When authorities arrived, he was seen standing in the driveway and they found Phyllis's body in the garage.

According to court documents, Frank told police he realized he had to kill his wife instead of moving her to an assisted living center because he feared she would live like a 'caged animal.'

He also told them that he could not put off the decision any longer and got a gun from his tool box and bullets from a filing cabinet.

Then, when his wife called for him to come inside the house, he told her to come into the garage, the Daily Advance reports.

He said as she walked toward him, he hid the gun from view then shot her in the chest twice.

Frank was arrested and initially held without bail.

He was originally charged with second-degree murder but pleaded guilty to voluntary manslaughter Wednesday in Pasquotank Superior Court.

However, he was not sentenced because he is undergoing treatment or a health condition that doctors say will take about eight months.

He is expected to be sentences at the end of the treatment.

Nazneen Ahmed, a spokesman for the North Carolina Department of Justice, said the shortest sentence for someone convicted of voluntary manslaughter is three years and two months.