OKLAHOMA CITY - An Oklahoma man accused of killing his then-Labor Commissioner father has accepted a plea deal that includes him being declared not guilty by reason of insanity.

Christian Costello, 29, was charged in connection with the fatal stabbing of Mark Costello in the parking lot of a Braum's in August 2015. An Oklahoma judge ruled that Costello should be evaluated by a state medical expert in August 2016.

“He will spend the rest of his life in a mental health hospital. There is no question in my mind,” says Costello’s Defense Attorney Bob Ravitz.

Oklahoma County District Attorney David Prater says this was the best possible outcome for everyone involved.

“You understand that this man had a complete break with reality and that he's severely mentally ill. It's no fault of his own,” Prater says. “Unfortunately, this brain disease has led to this young man to be incarcerated the rest of his life in a mental facility and his father was killed because of it.”

An initial forensic report determining Costello's mental competency stated that Costello understood the charges against him, but the psychiatrist who evaluated him said Costello has a severe mental disease, namely schizoaffective disorder, and cannot assist his lawyer with his defense.

The report revealed several disturbing comments Costello made about his parents, about his past mental health evaluations, and about his drug use, which included taking meth, marijuana, LSD, and other legal and illegal drugs.

The forensic report also stated how he felt his public defender was working against him - and felt his mother was paying his lawyer to work against him because she was upset that he killed her husband.

"He suffers from unbelievable psychotic episodes and psychosis," said Bob Ravitz, Costello's court-appointed public defender. "And these are things he can't change, and I think that's the way he is, and I don't think he knew what he was doing when he killed his father."

Costello claimed his father's murder was part of a military operation and claims it was an ordered hit.

"He is a very, very sick individual who has a tremendous history of mental illness, and tragically, he killed his father while in a psychotic episode and didn't know right from wrong," Ravitz said.

Costello's mother, Cathy Costello, issued the following statement soon after a plea deal was accepted:

Today the courts reached the best possible outcome and the Costello family is relieved to have this behind us.

Bob Ravitz and David Prater have our eternal thanks for their tireless efforts to reach a just and moral resolution and we are grateful for their concern and compassion. We are pleased justice was fairly served but we are still broken-hearted from losing Mark and Christian to the tragic reality of severe mental illness. 1 in 4 Oklahomans suffers with a mental illness and/or addiction — This issue affects everyone.

We pray for every Oklahoman who needs help to please seek treatment so no other families will have to suffer as we have.