The three friends no doubt thought shooting at an old lawnmower would be a fun way of exercising Americas gun ownership rights.
Mr Presley lost his left leg below the knee after being struck by the potentially lethal lumps of metal. The consequences could have been fatal if his friends had not been present to attend to his injuries and have him taken to hospital.
Tannerite, a patented product, combines ammonium nitrate and aluminium which are mixed and shaken together to produce an explosive. It is not flammable and generally stable when not subjected to high velocity bullets.
While its use for shooting practice is both common and legal in Georgia, the injured man and his friends ignored basic precautions, according to police - packing the lawnmower with too much explosive and then firing at excessively close range.
Its not a toy. Its much more than just a fire-cracker, said Joe Chapman, sheriff of Walton Country, adding that use of the explosive for fire practice generates frequent complaints about noise. As a rule of thumb, Im told that you need to be 100 yards away per pound of Tannerite.
Mr Presley admitted to be just 43 feet away from the lawnmower when he fired his high-velocity rifle. His two friends were standing behind him, one of them filming.