Murdered Children

Twenty children and a few adults were murdered yesterday in Newtown, Connecticut. The school Principal was among the victims. The violence occurred in Sandy Hook Elementary School at around 9:40 in the morning. Now, my point is this: when the Principal got up that morning - let's say around 6:00 a.m. - she had absolutely no idea that she would die later that morning. No clue whatsoever. In fact, even ten minutes before she died, she knew nothing about what was about to happen. Neither did anyone else who got shot and died. But God knew. He knows everything, even before it happens. God chose not to intervene. My question - and I keep asking this - why didn't God save them? God is all-powerful and saving the victims would have been absolutely no problem for Him. Why did He not save them? Anyone know?