Dust falls from a light fixture — which could indicate

a concussive blast from gunfire — before a Secret

Service officer appears to fire his first shot.

Dust falls from a light fixture — which could indicate

a concussive blast from gunfire — before a Secret

Service officer appears to fire his first shot.

Dust falls from a light fixture — which could indicate a concussive blast from gunfire — before a Secret Service officer appears to fire his first shot.

Sources: X/US Attorney Pirro, CNN reporting

Graphic: Way Mullery and Thomas Bordeaux, CNN