Looks like a second shooter could easily be in the building above the patsy. If not behind the window, then behind a sniper hole near the eave.
Don't forget a shot from somewhere took out the hydraulic line holding the speaker on the right.
Easy shot from inside the building above and behind the patsy.
The hiccups of the roof counter sniper is bizarre. He seemed ready to take the shot, then upsets, then shoots, and then disturbs his tripod for another shot? Per the theory, his only job was to silence the patsy.