A fake twitter account pretending to be the Archbishop of Salzburg claims that Pope-emeritus Benedict XVI has passed away in following tweet (archived here):
Mons. Georg Ratzinger confirmed me by phone that his brother Pope Benedict XVI has died minutes ago in the Vatican.
-- Franz Lackner OFM (@ErzbLackner) February 19, 2018
But the twitter account in question was only created last month and contains a tweet (archived here) announcing it is all a prank:
ATTENTION. This account is hoax created by Italian journalist Tommasso Debenedetti.
-- Franz Lackner OFM (@ErzbLackner) February 19, 2018
While we can't confirm at this time if Tommasso Debenedetti is really behind the account, the man has been famous for perpetrating various hoaxes through social media in order to prove how easy it is to do so nowadays.