Williams, Allan (2013-05-30). Operation Crossbow: The Untold Story of the Search for Hitler's Secret Weapons. Random House. ISBN978-1-4090-5173-2. In addition, there was evidence from foreign labourers who had been conscripted to work there and who began providing reports from early June 1943. One of them was twenty-year old Luxembourger Leon Henri Roth. who was exiled there after being caught starting a resistance cell. He successfully got letters through to his father, a member of a Belgian network, describing the rocket testing as sounding like 'a squadron at low altitude'. Unfortunately for the resistance hero, Roth would be killed by American army fire in 1945 while escaping with two Frenchmen in a German military car.