Replying to Telling on Somebody For Stealing

My brother tends to steal stuff if he wants it and I need some advice. He just stole 17 packs of Yu-Gi-Oh (He's 16, a bit geeky). That adds up to about 70$ total, which is quite serious. I don't know weather to tell my parents or not. I mean he's stole stuff before but not 70$ worth and this was from a walmart and usually he'll only steal from smaller places. I think If I don't tell my parents he'll keep stealing until he gets caught and he could get into some serious stuff for stealing. But I think if I do tell, he'll probably hate me and then my parents and him would get into this huge fight (and fights with him usually come to the point were he threatens to kill himself with knives, but he would never do that). What do you think I should do.