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Hypatia is one of my biggest heroes and one of the saddest stories I know (from Wikipedia):

Hypatia was the daughter of Theon, who was her teacher and the last fellow of the Musaeum of Alexandria. Hypatia did not teach in the Musaeum, but received her pupils in her own home. Hypatia became head of the Platonist school at Alexandria in about 400. There she taught on mathematics and philosophy, and counted many prominent Christians among her students. No images of her exist, but nineteenth-century writers and artists envisioned her as an Athene-like beauty.

In 391, Theophilus, the patriarch of Alexandria, ordered the destruction of some of the native Roman pagan temples in the city, which may have included the Musaeum and certainly included the Serapeum (a temple for the worship of Serapis and "daughter library" to the Great Library). In the same year Emperor Theodosius I had published an edict prohibiting various aspects of pagan worship, whereupon (although this was part of a wider phenomenon) Christians throughout the Roman Empire embarked upon a thorough campaign to destroy or christianize pagan places of worship.

Hypatia lived during a conflict between pagans and Christians, who were demanding the final destruction of paganism as an imperial institution. Hypatia, herself a pagan, was respected by many Christians, and was even exalted by a few later Christian authors as a symbol of virtue, often being portrayed by them as a virgin until her death.

Theories about the origins of the mob violence that ended Hypatia’s life range from a local, spontaneous Christian uprising tolerated by the Christian Patriarch Cyril of Alexandria over a conflict between Cyril and the city prefect Orestes; to a conspiracy by the Emperor himself; to a lawless, civilian "peasant stock" mob (soldiers are never mentioned) made up of Christians and non-Christians alike, led by a man named "Peter". Another point of view holds that Hypatia was part of a rebellion and her murder inevitable.

Basically she was murdered for religious and political reasons. She is one of the many Martyrs of Science. She died like so many before and after her, because she simply knew too much and was ahead of her times.

Some more information about the painting and the artist here.