The man suspected of shooting three people inside an Oklahoma City restaurant before being fatally shot by bystanders had no obvious connection to the victims or the restaurant, and was legally authorized to carry a firearm, authorities said Friday.

Investigators are trying to determine a motive behind the Thursday night attack that wounded four people, according to Oklahoma City Police Capt. Bo Mathews. He said the only interaction police had with the suspected gunman, 28-year-old Alexander Tilghman, was during a domestic assault and battery call when Tilghman was 13.

A police report from that 2003 incident indicates Tilghman was arrested after his mother told police he punched her several times during a dispute over a vacuum cleaner.

Mathews said Thursday's shooting appeared to be random but noted that Tilghman drove to the restaurant and wore protective gear for his ears and eyes.

"It looked like his mind was made up that he was going to discharge his firearm once he got there," Mathews said during a Friday news conference. Mathews stressed that the investigation was ongoing and confirmed that Tilghman's mental health was being looked into.

On a Facebook page that police said belonged to Tilghman, the man posts a video in which he claims his television is possessed by the devil. The page uses the same profile photo as a YouTube channel where a man that appears to be Tilghman also describes demons possessing his TV and being surrounded by computers.

He calmly begs for help from "a real human," saying he's suicidal, lonely and "really losing it."

The director of the LGBT rights group Freedom Oklahoma, Troy Stevenson, said Tilghman is the same man who distributed flyers across Oklahoma City earlier this year warning of demons taking over people's bodies. And a reporter with the LGBT publication The Gayly conducted an interview in January with Tilghman, who warned of "demons in cloned transexual (sic) bodies."

Flyers with similar messages were plastered all over a vehicle that Tilghman drove, said Ryan Beaulac, who said he frequently saw Tilghman at his apartment complex in northwest Oklahoma City.

Beaulac said he saw Tilghman acting strangely Wednesday night.

"He was twitchy, grabbing his hair and acting weird," the 35-year-old Beaulac said. "I was uncomfortable and definitely wanted to get away from him."

A man who identified himself as Tilghman's brother told television station KOCO that Tilghman needed mental health treatment, saying: "Nobody reached out to him, you know. He was crying for help."

Tilghman was licensed as an armed security guard, which authorized him to carry a firearm, said Gerald Konkler, general counsel for the Oklahoma Council on Law Enforcement Education and Training. The council certifies law enforcement officers and other armed personnel across the state. Obtaining such a license requires a background check and at least 72 hours of training.

A woman who answered the phone at the home believed to belong to Tilghman's mother declined to comment when contacted by The Associated Press.

Police said Tilghman was armed with a pistol when he opened fire inside Louie's On The Lake around 6:30 p.m. on Thursday. A 39-year-old woman and two girls were shot and wounded, while an unarmed man broke his arm while trying to flee.

All four victims were in good condition Friday, according to police.

Mathews, the police spokesman, praised the two citizens who retrieved firearms from their vehicles and shot Tilghman outside the restaurant.

"They were able to shoot the suspect and put an end to a very dangerous situation," Mathews said.

Mathews said it's unlikely either of the men, Juan Carlos Nazario and Bryan Whittle, will face criminal charges. Telephone and text messages left by The Associated Press seeking comment from the two men were not immediately returned Friday.

The Hal Smith Restaurant Group, which owns the restaurant, said the restaurant was closed Friday and counselors were available to employees and customers.

"We are extremely thankful the situation didn't escalate further, and that injuries were not more widespread. However, our hearts are with the wounded during this incident," the statement read.

The National Rifle Association said in a tweet Friday that the shooting was an example of "how the best way to stop a bad guy with a gun is a good guy with a gun."

In April, a restaurant patron wrestled an assault-style rifle away from a gunman at a Waffle House in Nashville, Tennessee. Four people were killed in that shooting. Police have said there would have been far more casualties if it weren't for the patron's quick thinking.

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This story has been updated to show that police say one of the citizens who shot the suspected gunman is named Bryan Whittle, not Bryan Wittle.