In the context of death that is meted out in the hands of heaven, the Gemara presents a list of those in this category - specifically, pertaining to the Temple, the required practices of the kohanim, and so on. Plus, other violations by kohanim while performing the Temple service who aren't punished with death, but simply with violating a negative commandment. Also, if a non-kohen eats terumah, reserved for the kohanim to be eaten with purity - seems a violation for lashes, and not worse. With careful inference with regard to the biblical text. Plus, the special status of Rav and his extra authority.