Sociopathic vampyres are real. They rule us, in fact, in the near-future alter-Earth. An oligarchical group, descendants of the 19th Century Robber Barons and the large plantation Aristocracy from the South (slavery was never abolished) have led Alt-America to full hemispheric conquest. Similar arrangements prevail in the British Empire, L'Afrique Française (Napoleon held on to Egypt, his descendants moved on South), the Deutsches-Ungarisches Kaiserreich in Europe and the Chin-Tsarist Empire in much of Asia.
Well, the bloodsucking part may be a bit metaphorical (although old Aztec practices have been revived in the Americas) and telomere regeneration vats might take the place of dusty crypts, and unnatural long-life is medically induced rather than transmitted by bites, but it is certainly restricted to a ruling class and their closest advisers and servants, which are feared as vamypres by the mostly ill-educated populace.
To give you a sense of how small a clique we're talking about, at the last Hallows Eve's Sacrifest, there were 12,000 adult American Vampyres in attendance, with another 20,000 present remotely using their Palantíri (we would call it Skype for Business, I guess). The Americas house a billion subjects.
The setting is a pseudo-anarchy libertarian nightmare fuel, with each of hundreds of noble families vying for power in the Great Game.
Assuming they have body-guards, and they don't age, have only slightly faster than human reflexes, senses and strength, but otherwise mortal like any other, how long can we expect such Vampyres to survive?