Emergency vehicles and personnel fill the parking lot outside of a Nashville-area theater where a gunman wearing a surgical mask opened fire at a showing of the movie "Mad Max: Fury Road" in Nashville, Tennessee August 5, 2015. [Photo/Agencies]

"There was dust flying everywhere," said plumber Sean Oliver, who heard a volley of shots and was able to see the back of the theater.

Three people were treated for exposure to pepper spray, including a 58-year-old man who also suffered a superficial wound to his shoulder, likely from the ax, Brian Haas of the Nashville Fire Department told reporters. None of the victims was taken to hospitals.

"This could have been a lot worse," Haas said.

A backpack that had been strapped to the man's chest was later detonated to eliminate any possible threat.

The shooting comes less than two weeks after a gunman opened fire in a movie theater in Lafayette, Louisiana, killing two people and wounding nine others before taking his own life.

The Tennessee and Louisiana shootings come three years after 12 people were slain and dozens wounded by a gunman at a cinema in Aurora, Colorado, during a midnight screening of the Batman film "The Dark Knight Rises."