Ronald Calvert, 50, was charged last December with the death of his mother, Joyce Philapy.
Calvert told investigators he was “sick of Philapy and tired of living with her.” When asked what he planned to do after leaving the home, Calvert replied he intended to kill someone else.
Police said Calvert stated he was taking Benadryl and that the drug made him believe he was somebody he was not.
Philapy died from blunt force trauma to the head and chest, according to Howard County Coroner Jay Price.
Calvert is expected to plead guilty to murder, but will use mental illness as a defense.