The metal brake line corroded away, and without warning failed completely. My truck was built in 2002 and during that time GM did not use stainless steal for the brake lines. Living in PA, we use salt on our roads during snow events. This salt corrodes away the non stainless steal break lines. If you have a GM vehicle made from 1999-2003, check to see if the SS was OEM spec. If not, have your shop check for any corrosion along the brake lines during the next service. If any is found, replace them with stainless steal lines. There are not many thing scarier than losing your brakes unexpectedly.