Helicopter falls out of the sky

Happened last November 29th in Glasgow, Scotland.  A police helicopter suffered twin engine failures, both engines quit, and the chopper fell onto the roof of a pub.  All three crewmen and seven patrons of the pub were killed.  Must have been quite a scene,  crowded pub, everyone hoisting beer mugs, and suddenly a helicopter busts thru the ceiling and crashes on the bar. 
   Accident investigation hasn't found anything useful.  Twin engine aircraft are not supposed to have both engines fail.  That's why there are two of 'em.  There was 5-6 gallons of fuel left in the tanks, enough to 10-15 minutes of flight.  Nothing wrong was found in either engine.  No radio distress calls were made.  The main and tail rotors had stopped turning by the time the helo hit the roof.  No evidence of an autorotation to a safe landing.  The chopper was just flying along, both engines stop, and it falls like a brick.  No one knows why.