Battlestar Galactica
There are only a few TV series that start with the annihilation of humanity. Among the more well-known ones, perhaps only The Walking Dead can be mentioned.
Although people there are not actually wiped out, they just adjusted their eating habits and lost some cognitive functions.
In Battlestar Galactica, humanity simply disappeared. Their change of state was mainly aided by atomic bombs, which were dropped on them by their own creation – the Cylons.