What do I tell my Best friend need advice FAst!?

My best friend has been in a situation where she lives with a boyfriend/ engaged too and hes got a needy personality. When she ever brings up leaving him or breaking up with him he starts crying and saying he cant live without her. Than since he owns guns he will say well I will end my life. Then she will tell him no dont I love you they make up. Then he tells her I would never kill myself Im not like that Im sorry, She feels better with him. A month later there at it again but this time he gets a gun out and acts like hes looking for abullet to put in it. But not shoot her but himself. Says I cant live without you . Crys, than she makes up with him. Now shes full of emotions wanting to break it off, but scared to worried if he really would hurt himself. Doesnt know who to go to. She told me but I promised her I wouldnt tell no one. Shes not scared of her life at all, says he wouldnt ever touch her, Acts like he really does love her alot,. The only reason she ever brings up breaking up with him is when they start to fight and talk about the family drama they have is splitting them up. What do I tell her to do? Im soo freaking worried.