On the night of 23–24 August 1572, while many prominent Protestants from all over France were in Paris on the occasion of the marriage of Henry of Navarre—the future King Henry IV—to Margaret of Valois, sister of Charles IX, the royal council decided to assassinate the leaders of the Protestants. The targeted killings quickly turned into a general slaughter of Protestants by Catholic mobs, known as St. Bartholomew's Day massacre, and it continued through August and September, spreading from Paris to the rest of the country. About three thousand Protestants were massacred in Paris and five to ten thousand elsewhere in France.