An 18-year-old woman was accidentally shot in the knee with a BB gun in the Walmart parking lot at the base of Signal Mountain Tuesday morning.

The injury is believed to be non-life-threatening.

It’s not clear yet if the injury was self-inflicted or if another person shot the victim.

BB guns, often regarded as toys, can inflict serious wounds. Current weapons look much like their more traditional counterparts.

The muzzle velocity of an air-powered BB gun can approach 750 feet per second; a 9mm round (the world’s most popular ammunition caliber) has a muzzle velocity of over 1,100 feet per second.