Plot summary issue: sniper scope tampering 

The plot summary states the following:
Unbeknownst to the Doctor the assassin is actually among the delegates. He pulls out a pistol  when the Doctor reaches the camera level and shoots the President dead. The crowd sees the Doctor on the catwalk firing the sniper rifle (in an attempt to stop the assassin) and assume he is the killer.
I don't think this is correct.  The cut when the Doctor fires strongly implies that it is HE who shot the president (a fake-out that's the focus of the cliffhanger, in fact), and not the man in the crowd.  Also, it's later revealed that the scope on the Doctor's sniper rifle was tampered with.  I'll have to go and check, but it's always been my impression that the scope was tampered with in just such a way that when the Doctor attempted to fire on a would-be assassin in the crowd who was standing in just the right spot, his staser bolt would hit the president instead, in a perfect frame-job. 76.126.142.59