Thietmar of Merseburg
In 1003, when the Vršovci tried to dethrone Boleslav III the Red. When the expatriated duke returned to Bohemia possibly with the support of Duke Bolesław I the Brave of Poland, he ordered a massacre of the Vršovci at Vyšehrad. According to Thietmar of Merseburg, Boleslav slashed to death his son-in-law (Vršoviec) with his own sword during Lent.