He was 13 at the time.
Police say the two men had arrived at the restaurant separately, and saw the man open fire. Three people were shot: Natalie G. Niles, 39, and two unidentified girls.
A large number of witnesses are being interviewed, authorities said.
Multiple people were injured in a shooting in Oklahoma City on Thursday evening. As OCPD has reported, the suspect is dead.
Mathews told The Washington Post that the shooting "appears to be a random act", but it remains under investigation.
Matthews says police "have no reason to believe this is a terrorist type of incident".
Capt Mathews said the suspect, Mr Tilghman, shot at customers from outside the door of the restaurant, adding that "it could have been really tragic" if the gunman had actually entered the confined space. Both the gunman and the bystander who intervened used handguns in the shootings, Mathews said.
Will said he doesn't know if his daughter knew the shooter, but that he would like to thank the passer-by who authorities say shot and killed the gunman as he left the restaurant.
In all, officials say there were four people who were injured as a result of the shooting.
The Republican governor recently vetoed a state bill that would have allowed adults to carry a firearm without training or a permit.
The statement referred other questions to police. A possible motive hasn't been released.
The victims who were shot have been taken to a hospital with serious injuries.
Another woman also was wounded by gunfire, and a man fell and broke his arm after Tilghman began his assault, police said.
Mathews said it's unlikely either of the men, Juan Carlos Nazario and Bryan Whittle, will face criminal charges.
The Hal Smith Restaurant Group owns the restaurant. He was shot and killed outside by an armed civilian with a handgun, police said.
A gunman opened fire on a restaurant in Oklahoma on Thursday, but he met a swift end when a "good Samaritan" opened fire on him outside of the restaurant.
The shooter, a white man, opened fire at Louie's Bar and Grill about 6.30pm, and struck the family, who had been going out to celebrate a birthday, before trying to flee the scene.