Tearing keriya - rending one's clothes. For whom do we tear? Starting with father, mother, and teacher - as learned from the prophet Elisha and his relationship with Eliyahu. Plus, tearing keriya as mourning for the Beit HaMikdash. Also, the specifics of tearing keriya for more than one person at once - which may have been as horrific as it sounds, or perhaps the Gemara is exploring the parameters of tearing keriya, though it sounds morbid. Plus, when the tear can be mended afterwards (but not with regard to one's parents).