Mark Costello's son, Christian Costello, was arrested for his father's bloody murder on Sunday. The commissioner's son, who allegedly committed the murder, had been suffering from mental health issues for years, Tulsa World reported.

The son met with his parents at Braum's in Oklahoma City, but the meeting turned into a gruesome incident when the mentally ill son attacked his father and followed him outside the restaurant to stab him multiple times in the head and neck. Witnesses say the mother tried to stop her son from committing the crime, which HNGN previously covered.

The Costello family released their statement on Monday afternoon that they could not express the "shock and sadness" brought by the situation. They said that the 26-year-old suspect has "struggles with a mental health disease," and "Mark was committed to being there for his son and provided whatever help he could as a father," according to The News & Advance

Following a plea over a DUI charge in 2012, the son once spent 90 days in a mental health facility to treat his undisclosed mental illness. There he took mood stabilizers, according to court records acquired by the Associated Press, The News & Advance reported.

"What set him off to attack the commissioner, we still don't know," Capt. Paco Valderrama of the Oklahoma City Police stated at a conference.

Mark Richardson, the man who lived across Christian Costello in a condominium complex, said he saw him talking or dancing alone. "We've seen him walking around aimlessly all the time," he said. "He'd walk around half the time with hardly any clothes on."

A hearing is set for the younger Costello on Tuesday before Special Judge Russell Hall for a bond hearing via video link from the Oklahoma County Jail. The bailiff Linda Waco says that the Special Judge will highly likely deny the son of the bond due to the extent of his crime, Associated Press reported.

A rosary for Mark Costello will be held at St. Monica Catholic Church on Friday, Aug. 28 at 6:30 p.m. local time and the funeral mass will be at the same church on Saturday, Aug. 29 at 10:00 a.m. local time, according to KFOR News Channel 4.