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The ominous sound of a 12-gauge shotgun

15 October 2012 Last updated at 00:40 BST

Panorama reporter Raphael Rowe visited Al's Army Navy store in Sanford, Florida - the town where Trayvon Martin was fatally shot in February - to find out about the type of weapon customers prefer for self-defence.

General Manager Fred Meltzer explained the appeal of a 12-gauge shotgun, loaded but not quite ready to fire.

Panorama: Kill at Will? America on Trial is on BBC One, Monday, 15 October at 20:30 BST and then available in the UK only on theBBC iPlayer.