What would the line of sight be like from inside the building? Anyone tried to model that using Google Earth 3d? Same with the water tower - would shots from that direction match the ballistics of anyone who got shot?
Official word is that the SS team inside the building were using it as a spotting location. The fact that this was released means, IMO, that it unlikely to be them. My experience of previous "lone shooter" events that obviously had multiple shooters is that there is only ever oblique or vague eyewitness references to them, plus circumstantial evidence pointing to multiple shooters. Even if they get caught by local cops, they never really get caught.