By Heide Brandes
OKLAHOMA CITY (Reuters) - The son of Oklahoma's state labor commissioner is being held on suspicion of fatally stabbing his father at a fast food restaurant in Oklahoma City, police said on Monday.
Commissioner Mark Costello, a father of five children, was seen stumbling out of a restaurant in the northwest part of the city on Sunday and was taken to a nearby hospital where he was pronounced dead, police said.
Christian Costello, 26, has been arrested in connection with his father's death, Oklahoma City police captain Paco Balderrama said.
According to police, two witnesses said they used their vehicle to knock Christian Costello down as he chased his father through the parking lot and jumped him.
Police said Costello and his son had an argument, but agreed to meet and try to reconcile earlier on Sunday. The conversation at the restaurant grew heated and Christian Costello pulled a knife and started stabbing his father, police said.
Police do not know where the knife came from and do not know what "set Christian off," Balderrama told a news conference.
Balderrama said police believe they have Costello's attacker in custody, although it could take several weeks to file charges. The information from the investigation will be turned over to the district attorney to determine charges.
Balderrama said police interviewed 17 witnesses on Sunday night and needs to speak to more.
"We need to look at surveillance video and collect all the information," he said.
Costello was elected to run the state's Department of Labor in November 2010, according to a state website. He and his wife, Cathy, have been married for 33 years.
Governor Mary Fallin said on Monday that flags on state property will be flown at half-staff through the end of the week in honor of Costello.
(Reporting by Heide Brandes in Oklahoma City; Writing by David Bailey; Editing by Lisa Lambert)