That is a manifestation of the disease which occurs in genetically predisposed individuals and pregnant women etc, with the common Variola major strains. I haven't heard of any distinct strain of Smallpox with such a high mortality rate against vaccinees. But I have heard of vaccinated people who were infected with India 1 becoming very ill.
The Soviets were testing smallpox aerosols at their main bioweapons testing range, Vozrozhdeniye Island in the Aral Sea in 1971. Apparently, a young female biologist working on deck aboard a research ship which was passing by, was infected. She came down with smallpox later in the port town of Aralsk. A total of twelve people there became ill, the town was quarantined and 50,000 people were re-vaccinated.
The three who died, a woman and two small children, had never been vaccinated. The rest had been, and although they fell ill, they survived.
Apparently, the Soviet Smallpox strain was isolated in 1967 in India during a vaccination program by Soviet medics. The strain was so deadly to non-vaccinees the Soviets decided to use it for their bioweapons program. They also tried to genetically engineer it, so that standard Vaccinia virus would not be an effective vaccine - but failed. Hopefully, no budding al-Qaeda Molecular Biologist has succeeded where the Soviets failed!
I too had read about the smallpox outbreak near the Aral Sea in 1971, and how the hurried vaccinations saved lives. Very encouraging.