What will make this man behead his Mother

This man was caught with his mother's head, while he was about to dispose her away secretly. The culprit who was identified as segun Odihiri of 36 years old, revealed that, he was about to rape his sister when the mother identified as Maria Odihiri of 83 years old from  Uzzeba, Owan West LGA of Edo

State caught him, and started screaming out loud to notify the public of his evil doing.
In an attempt to cover his illicit act, picked up a cutlass and chopped off his mum head. While the sister ran for safety.