OKLAHOMA CITY - A man was arrested on a complaint of first-degree murder in the stabbing death of his father, Oklahoma Labor Commissioner Mark Costello.

According to police, at 6:35 p.m. Sunday, officers responded to the report of an assault in progress at the Braum’s restaurant, located at 11224 N. May. When officers arrived, they found the victim, later identified as Labor Commissioner Mark Costello, stabbed multiple times and sitting in a vehicle.

Officers rendered aid to Costello until EMS personnel arrived and took over. He was transported to an area hospital where he died of his injuries.

Police arrested 26-year-old Christian Costello, who was being detained by witnesses in the parking lot of the restaurant. Christian is Mark Costello’s son.

Earlier in the day, police said Commissioner Costello and Christian Costello agreed to meet at the restaurant. While at the restaurant the meeting turned violent and Christian Costello pulled out a knife and attacked Commissioner Costello.

“We are investigating where the knife came from. We do know it was in his possession when he was meeting with dad,” said Capt. Paco Balderrama during a news conference Monday morning.  

According to police, the incident continued into the parking lot as Commissioner Costello tried to run away from his attacker. However, police said Christian Costello managed to stab his father multiple times, causing his death. Police said Commissioner Costello was stabbed at least once in the head. 

Capt. Balderrama said several witnesses were in the parking lot during the incident. They used their vehicle to knock the attacker down and removed his weapon. Police said witnesses held the suspect down until officers arrived. 

Christian Costello was arrested for first-degree murder and has been booked into the Oklahoma County Jail.

According to Capt. Balderrama, Commissioner Costello's wife was also in the parking lot at the time of the incident. She tried to intervene, but was unsuccessful. 

The Oklahoma City Police Department has been in contact with representatives from the Labor Commission and they will have counselors on hand Monday morning to tend to the emotional needs of Commissioner Costello’s staff.

Commissioner Costello’s death is Oklahoma City’s 54th homicide of 2015, according to police. 

Capt. Balderrama said police are gathering all the evidence they can before they present the case to the District Attorney, who will then determine what charges to be formally filed. Officers spoke with about 17 people at the scene Sunday night and they processed both crimes scene inside and outside the restaurant. 

Oklahoma Governor Mary Fallin released the following statement regarding Oklahoma Labor Commissioner Mark Costello’s death:

“I was shocked and greatly saddened to hear of Labor Commissioner Mark Costello's tragic death last night. My prayers and deepest sympathies go out to his family, friends and staff. Oklahoma has lost a dedicated public servant and a good man.

In honor of Mark’s life and his service to the state, all flags on state property will be flown at half-staff through the end of the week.”

In an address to the media on Monday, Fallin said a replacement for Costelloe will be named "at the time that is appropriate. The Governor also ordered all flags to be lowered to half-staff until Monday, Aug. 31.

A statement was also released on behalf of the Costello family:

"There are no words to express the shock and sadness that our family has experienced the last number of hours. The outpouring of emotion and support our family feels is tremendous.

Our son, Christian Costello, has experienced many difficulties over the past several years. Christian, like thousands of Oklahomans, struggles with a mental health disease and like many families we did our best to support him. Mark was committed to being there for his son and provided whatever help he could as a father. 

We ask for your prayers and support as our family tries to cope with and understand this life-changing tragedy.

Mark loved to brag about his kids and their successes, but like many in the public eye, he also viewed his family life as personal. We ask that you respect our family's privacy as we work through this very difficult time and please understand that our family will struggle with this for years to come as we try and find answers."