Oklahoma's labor commissioner was stabbed to death at an Oklahoma City restaurant Sunday evening and his son was arrested on a first-degree murder complaint, authorities said.

State Medical Examiner's Office spokeswoman Amy Elliott confirmed to the Associated Press that Mark Costello, 59, was the victim of the stabbing at a Braum's ice cream and fast food restaurant on the northwest side of Oklahoma City. A spokesman for the Labor Department also confirmed Costello's death.

"Our hearts ache as an agency for this tragic event and our department grieves for his family during this very difficult time," Labor Department Chief of Staff Jim Marshall said in a statement.

Oklahoma City police Lt. Alex Edwards told NewsOK.com that the stabbing took place at approximately 6:30 p.m. local time. Witnesses told police Costello and his son, 26-year-old Christian, got into a heated argument that became violent.

Christian Costello was arrested at the scene. Authorities say Christian Costello used a steak knife to stab his father. Officials told KOKH-TV that Mark Costello was stabbed at least four times and was seen stumbling out of the restaurant. 

"He made his way around the Braum’s seeking help," Edwards said. "He then went outside to the south of the restaurant and was confronted again." Edwards said the elder Costello was stabbed again before bystanders subdued his attacker.

Mark Costello was pronounced dead at a local hospital.

NewsOK.com reported that father and son had met at a restaurant to reconcile after having an argument earlier in the day.

"I'm just numb right now, as many of us are," Oklahoma Republican Party Chairman Randy Brogdon said. "He was a great Christian, a good man and a wonderful husband and dad. He is going to be sorely missed."

A successful businessman from Bartlesville who founded a telephone software company in 1984, Costello ousted the incumbent Democrat Lloyd Fields during a Republican sweep of statewide offices in 2010. He easily won re-election in 2014. He and his wife had five children.

"My family is stunned and deeply grieved to hear of the tragic death of Labor Commissioner Mark Costello." Sen. James Lankford, R-Okla. said in a statement. Mark was passionate about our nation, conservative fiscal principles, and the people of our state. Mark was a friend, and as we grieve, we will also pray for his family as they deal with this unbelievable tragedy."

A strong proponent of smaller government, Costello closed the agency's Tulsa office, which he said was underused and that the agency's technology upgrades had allowed much of its professional licensing services to be conducted online.

"You can reform government," Costello said during last year's campaign. "It can be done when there is political will. I have that political will."

The Associated Press contributed to this report.