Vegas was a single shooter and here is the simple explanation.

Here is HealthRanger's analysis. Most of the "home learned" people seem to agree and the math itself adds up. Not knowing all the variables there is a possibility for error, but based on this type of videos AND what I hear in the videos, I am quite sure personally there are at LEAST two gunners. Might be three.

Then again, the whole thing seems like one more falseflag-psyop, so it's very possible some (or all) of the audio is from weapons shooting blanks or comes from external audio devices/speakers even. It would not take many "crisis actors" to cause the panic and play "victims", and the mass panic would make sure there would be hundreds of "real" eye witnesses telling us what they saw. As they would have not known that some (or all) of the victims were actors, they would absolutely believe there was a massacre and saw "a lot of people being killed or hurt".

However one has to point out that so far almost every "witness" I've seen in the MSM screams (crappy) crisis actor rather than a believable eye witness, so..

It's SOP for a sniper to stand back from a window opening to reduce their visibility.