Complex sentence: From the beginning the murder weapon was presumed to be an iron pipe, bought the day before the murders by von Sydow's son Fredrik von Sydow, but it was determined later that a flatiron that was missing after the murders was the actual murder weapon.
Split into simpler sentences: From the beginning the murder weapon was presumed to be an iron, bought the day before the murders by von Sydow's son Fredrik von Sydow. But it was determined later that an iron that was missing after the murders was the actual murder weapon.