Unfortunately, I know this for a fact (I'm from Israel, talked to people who were there). It's not even the worst thing that was done. As Israel is torn between protecting the victims of the attacks and explaining them to the world, the proof you require will probably never be shown. I assume you are familiar with the "Hamas horror film"? Is what it shows not enough to go to an all out war against an enemy that has very clearly shown its only goal is your total destruction?