This is exactly why I make sure I'm not drinking anything when I am reading posts on this forum! You never know when you could end up giving your computer a bath!
The avg person is not trained in how to deal with situations like this. Lack of training and fear more than likely kept them at bay. The woman was brave and attempted to distract or dis-arm him. There was a split second where the window was there, but how many people on a school board do you think has had the training in dealing with situations like this? The human brain has a flight or fight syndrome built into it. Most people do not know how to channel the fear to use it because of the lack of training. Fighters and martial artists are trained to re-act to a situation and if trained properly and long enough it becomes a reflex and not something they have to think about.
The most probable training out of a group of people like that would be psychology and the last things on their minds would be rushing a gunman. The gunman appears to have a death wish and I think that he did not intend to hurt the hostages. Notice he released the females. If I was to take a hostage a female would be a better leverage. He also turned his back to security and most are police officers with weapons in today's school systems. I think he for whatever reason he wanted to end his life, but did not want to do it. He put himself in a situation where he knew he would be taken out eventually. He had stated he had already been in prison. The firearm alone was a probation violation. Discharging it he knew there was no way out other than death or going back to prison.
It is very easy to watch that and decide what one would do. It is much harder to be involved in that and remain calm enough to know what to do. It is possible that by rushing him that someone would have been hurt or killed then the aftermath of living with that move if someone else was killed would be a lifetime of coping on did I do the right thing? The same could have went if no one reacted and he killed someone. The shock of the situation is what kept fear as a factor. Police and military personnel go through extensive training in situations like this. Not the avg joe in this situation.