Four people were killed and two others critically injured when a man naked from the waist down and wielding an AR-15 assault-style rifle opened fire at a Waffle House in Tennessee early Sunday, police said.

The suspected gunman was identified as Travis Reinking, 29, from Morton, Illinois. He was arrested in July for allegedly breaching a barrier at the White House and demanding a meeting with President Donald Trump, officials said.

Reinking had also threatened to commit suicide in May 2016 in a parking lot in Illinois and at the time his family told authorities he was having "delusions" involving Taylor Swift. He believed the singer was stalking him and harassing him, according to police records obtained by ABC News.

PHOTO: Metro Nashville Police Department experts investigate the scene of a shooting at a Waffle House near Nashville, Tenn., April 22, 2018. (Metro Nashville Police Department) More

Early Sunday, Reinking ran from the scene after a patron at the restaurant wrestled the rifle away from him, police said. Police on Sunday evening were using dogs and a helicopter to search a wooded area near the restaurant where the gunman was last seen.

"He's murdered four times with no apparent reason, no apparent motive. So we're very concerned," said Chief Steve Anderson of the Metropolitan Nashville Police.

Anderson said a pistol belonging to Reinking had not be recovered and he should be considered armed and dangerous.

A witness to the shooting, Chuck Cordero, 50, told ABC News that he had just pulled up to the Waffle House in Antioch, a suburban area about 12 miles from downtown Nashville, when gunfire broke out.

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"He was only wearing a jacket and nothing else on," Cordero, a roadside-assistance worker, said of the gunman.

Police said two of the dead were shot outside the restaurant and one inside. A fourth person who was shot inside the restaurant later died at the hospital.

Two other people shot in the incident were in critical but stable condition at Vanderbilt University Medical Center in Nashville. Other victims were struck by shattered glass.

The person who wrestled the rifle away from the shooter is a "hero," police said.

Cordero used the same word.

"There's a hero," Cordero said. "I don't know what his name is, but there's a gentleman who was in there, who when this guy stopped to reload or stopped to do something with his gun, he took that opportunity and wrestled the guy till the gun went flying and then the dude took off running."

"I talked to him afterward and told him, 'You are a hero, man,' because had that guy reloaded, there were plenty more people in that restaurant," he said.

But the courageous patron, identified as James Shaw Jr., 29, refused to call himself a hero.

PHOTO: James Shaw Jr., 29, shows his hand that was injured when he disarmed a shooter inside an Antioch Waffle House, April 22, 2018 in Nashville, Tenn. (George Walker IV/The Tennessean via USA Today Network) More

"I just knew it was me or him. It was that type of scenario," Shaw said at a news conference Sunday afternoon. "So I chose to go with what I wanted to go with and it worked."

Shaw said that when the gunfire broke, a bullet grazed his elbow as he ducked for cover near the restaurant's restroom. He said that when he saw the gunman look down at his weapon apparently to reload, he made his move.

"It was at that time I kind of made up my mind ... that if it was gonna come down to it, he was going to have to work to kill me," Shaw said.

Cordero said there were about 30 people in the restaurant at the time of the shooting.

He said the first victim, identified by authorities as Joe E. Perez, 20, of Nashville, was killed at the front door of the restaurant. Cordero said the second victim was a friend, a cook at the Waffle House identified by police as Taurean C. Sanderline, 29, of Goodlettsville, Tennessee, who was outside on a cigarette break when he, too, was fatally shot while trying to run from the gunman.

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