applied arm lock would get that bully to kiss the street. we didn't have to run from him anymore. >> reporter: when he grew up, weldon enlisted in the marine corps. after leaving the service he worked as a firearms instructor. >> a customer walked in. i could tell something was wrong with her. i couldn't tell exactly what, but i could read that she was under some kind of stress. >> her name was crystal harris. >> he was like, can i help you? i said i need to buy a gun. i said it's not just for putting it away. my life is in danger. and it's from my husband. and he was like, whoa. >> crystal, a mother of two young sons told weldon her husband was violent and abusive. she wanted to buy a gun for protection. >> so at that point i asked her, are you prepared to kill him?