After Nazi Germany's capitulation in May 1945, the Police branch of the Royal Air Force, with whom the 50 airmen had been serving, launched a special investigation into the killings, having branded the shootings a war crime despite official German reports that the airmen had been shot while attempting to escape from captivity following recapture. An extensive investigation headed by Wing Commander Wilfred Bowes (RAF) and Squadron Leader Frank McKenna of the Special Investigation Branch into the events following the recapture of the 73 airmen was launched, which was unique for being the only major war crime to be investigated by a single branch of any nation's military.[1]:261