telewinz, please correct your erroneous statement. Here's the sketch that sniper Lon Horiuchi himself drew during an initial FBI interview.
No curtains, two heads behind the window.
The following narrative is from Gerry Spence's book:
And, of course, we remember that Lon Horiuchi, who had taken the stand, had testified that, indeed, he had intended to kill Kevin Harris, who was running for his life, his back to the sniper. Yet the prosecution claimed that the sniper, who admittedly could see and hit a fly at two hundred yards with his ten-power scope, could not see the head of Vicki Weaver through the glass window of the open door. Instead, the prosecution attempted to make the jury believe that the curtains were closed. But from my own discussion with Randy that fact seemed in question, especially after the government failed to produce a crucial Horiuchi drawing of what the sniper had seen when fired.
From the drawing made by Horiuchi during an interview with the FBI at a hotel, on hotel stationery, he draws in no closed curtains at all. In the lower right-hand corner of the window we see two partial heads as if people were squatting there. Indeed, Randy and Sara had dived into the house just ahead of Kevin Harris. And it was Harris, not Weaver, who presumably had killed a federal officer, and who Horiuchi himself was admittedly trying to kill, whether or not he was carrying out the unwritten law that seemed to doom the cop-killer. Be that as it may, the method of hitting a running target is for the shooter to place the "mildot" seen in the scope on the target -- harris in this case -- which places the crosshairs ahead of the target, thus leading the target, so the bullet and the target will arrive simultaneously. Shortly after the killing this is exactly as Horiuchi himself drew it for the FBI interrogator.
Horiuchi's drawing shows us that he must have known that human beings were behind the flimsy door. He had to know that someone, presumably Vicki or ten-year-old Rachel, was likely standing behind the door to hold it open. Moreover, the drawing proves he knew exactly where it did strike -- at the cross, as he shows it in the drawing. Vicki Weaver's head was behind the cross, that apocalyptic symbol, which served also as the point of aim for the killer.