French Prime Minister Manuel Valls said early Thursday that “several arrests” were made overnight while police were searching for two men suspected of killing 12 people in an attack on a satirical newspaper. Police are seeking suspects Said Kouachi, 34, and Cherif Kouachi, 32, in connection to the terrorist attack on the Charlie Hebdo offices in Paris on Wednesday. Hamyd Mourad, the 18-year-old getaway driver, turned himself in late Wednesday. President François Hollande declared Thursday a day of national mourning while flags across the country are expected to be flown at half mast. The government buildings will hold a “moment of reflection” at noon while a ceremony will be held in the courtyard of the National Assembly in Paris. Notre Dame Cathedral has planned a special Mass in honor of the victims.