That Greedo explanation is bullshit. The script says that Han fires first. Then its filmed so that Han fires first. Then its edited that Han fires first. Theres never any ambiguity about it. The only thing about it was a stylistic suspense device--you see a flash of a lazer and a burst of an explosion and its cut so fast that it becomes impressionistic--then the smoke clears and Greedo is dead and Han is the last man standing. Thats how the script describes it and you can even see in the finished film that thats the way its clearly edited, and it is specifically structured that way because thats a western genre cliche that Lucas was trying to evoke. Even Gary Kurtz has recently said something to the effect of "Lucas' explanation on its filming doesn't make sense because the scene was designed and filmed with Han firing first and it would have been very easy to film it with Greedo firing first if thats what he wanted." It also would have been even easier to "fudge it editorially" as Lucas has put it. But theres only one laser blast, one laser sound, and a very clear sequence of shots showing Han blowing him away.