"I cannot believe that such a well trained and disciplined force would fire on innocent, unarmed civilians."

Maybe that depends what the training has included, and how the discipline is directed. When it comes to being "a well trained and disciplined force" the British paras score pretty high...

I can't see how using heavy machine guns against a civilian crowd could ever be an appropriate response, even if there had been some guys with rifles. Some of the people killed weren't even in the crowd, they were in their homes across the street.

Someone "offered" them the use of the school? I can't quite see that happening.