The Cheektowaga man accused of killing his father last April has agreed to a plea of not responsible by reason of mental disease or defect.

SirWilliam Hardy, 31, was originally charged with second-degree murder in the death of his father, 54-year-old William Hardy, in his Whitney Place home. His father was visiting from California.

Erie County District Attorney John Flynn says SirWilliam, who was paralyzed in an accident several years ago, had a video surveillance system in his home. Footage from those cameras showed there was no argument between the men before SirWilliam shot his father twice with a rifle.

"Devastating for the family to have a son shoot his own father," said Flynn. "It was a terrible evening and a terrible event."

Psychiatrists later determined SirWilliam suffers from schizophrenia and delusional disorders.

"You can see from the video clearly that SirWilliam Hardy was acting as two different people," Flynn said.

Prosecutors, the judge and SirWilliam’s defense attorney agreed he did not understand the consequences of his actions at the time of his father’s death.

"The family apparently at one point tried to get him to go see someone professionally," Flynn added. "There was some indication from the family that he was acting in a bizarre manner before this occurred."

SirWilliam will be transferred into the custody of the New York State Mental Health Office for later placement in a secure psychiatric facility.