Hunt for 'naked' gunman after four killed in Nashville Waffle House shooting

A manhunt is underway after four people were killed in a shooting at a Waffle House restaurant in Nashville.

Local police said authorities are searching for 29-year-old Travis Reinking who was reportedly wearing nothing but a green coat when he stormed into the diner just before dawn on Sunday.

Officers in Tennessee called a customer who wrested the weapon from the gunman, a "hero".

Two other people were being treated there for gunshot wounds, with one in critical condition.

Police spokesman Don Aaron said the gunman arrived at the restaurant, sat in the car park for four minutes and shot two people with an assault rifle.

The gunman then went inside and continued firing.

A 29-year-old male customer grabbed the rifle from the suspect and tossed it over a counter, Mr Aaron said.

"No doubt he saved many lives by wrestling the gun away and tossing it over the counter and prompting the man to leave," Mr Aaron said.

The suspect, wearing only a green jacket, shed the jacket after fleeing the restaurant.

Nashville mayor David Briley said the shooting represents "a tragic day" for the city.

"My heart goes out to the families & friends of every person who was killed or wounded in this morning's shooting. I know all of their lives will be forever changed by this devastating crime," Mr Briley said on Twitter.