(NEWSER) – Dzhokhar Tsarnaev told investigators that he and his brother originally planned their attack for July 4th—but they built their bombs so quickly that they moved the mission up to the day of the Boston Marathon, reports outlets including the New York Times, Boston Globe, andCBS News. All of the accounts are based on anonymous law-enforcement officials. Dzhokhar reportedly said the brothers first wanted to attack Boston's July 4th celebration on the Charles River. But when the bomb-making went so smoothly in Tamerlan's Cambridge apartment, they drove around the city casing police departments to attack, says the Globe. Eventually they settled on the marathon—Patriots' Day in the state.