Who would be held responsible for such a horrific act?

Black September - at first notice I would think that this would describe a dark month in a countries history. Yet to this very day this name still lingers on. Black September or as it is formerly known, The Black September Organisation was a Palestinian paramilitary group (which basically means that the group was organized to function both politically and to assist the military, kind of like a militarized sub-unit). It was founded in 1970. This was the very group that was responsible for the horrific attack that occurred on the day of the 5th of September, 1972. It is somewhat of a sub-division of the PLO (The Palestinian Liberation Organization).