First off, I recommend perusing the forum for discussions on ontology, free will, and predestination, as those subjects are absolutely critical to a treatment of your question. I will provide an answer based upon my personal understanding of the issues involved. There are many sources throughout Rishonim, Achronim, and modern rabbis who talk about this and there are shivim panim le'Torah, especially in this regard. So there are plenty of source for and against any given opinion.
I'm also going to steal something I wrote previously for a burial that is very pertinent to this question.
Okay, now on to the meat of things:
When we talk of God being beyond time, there are many interpretations of the how we handly those implications. Does he "walk through" time at will like you or I would travel through space? My understanding is that God occupies a higher (or infinite, or beyond infinite, what have you) mathematical N-space. If you were to take your three dimensional self and consider the extension of your body through time from the moment of your birth until your eventual death, that unit would be your four dimensional self. A being in a higher dimension wouldn't see you "going about your day" in a linear, time based manner - they would perceive you and the sum of your choices like you view the contours on an object - as an indivisible part of the whole.
To put it another way:
Does your current knowledge of what you did yesterday impede your free will yesterday? No, because those actions have already occurred from your perspective in time. God does not view time linearly. So when he creates/created the world, it wasn't just at the moment of Genesis, but rather the whole of existence from start to finish. We only perceive creation linear because we are bound to this lower order of existence, which is why we state that "He renews, in his goodness, the creation each day." We also states that Hashem sees "From one end of the world to the other and from the creation of the world to it's end," that "a thousand years are identical to a single passing day in your eyes," and many others that point to this form of transcendence.
This means that God's knowledge of our future actions isn't a violation of freewill because, from the divine, nonlinear perspective, you have already acted.
Now to answer your question...
There are many who would posit that, yes, if September 11th hadn't happened then those victims "would have died anyhow in some other way." But this is true only if you are looking at "destiny/fate" from a linear perspective, so these people were "fated" to die. According to a non-linear perspective, not only is freewill completely free and preserved, the impact of your freewill is uniquely preserved as well. Your future actions are integral to the form of creation in "our past," since from Hashem's perspective they exist simultaneous to the moment light was "let."
SHEHAKOL NIHIYEH BIDVARO: This is the only bracha we regularly recite that ISN'T in past or present tense. We don't say that everything IS or HAYU - WAS, only NIHIYEH - that it WILL BE. Not only that, but it's in first person PLURAL- WE will be according to his word. What is going on?!
Intrinsic to this bracha is a recognition that, in the present tense, all is not (or doesn't seem) "according to plan." Things that should never have been, are, and the world that was supposed to exist vanished. The expulsion from Eden, the spies in the desert, Moshe hitting the rock. Turning points where the brighter future was made distant, where the path was rerouted into two thousand years of exile, pogroms, the fires of the Holocaust, and a nation purchasing it's survival with the blood of its children and the tears of its parents. We lost the world that was, and this is not a world that should be. But it is still a world that CAN BE, because we can still become something greater. So we remind ourselves that hope is never fully lost, it is only deferred.
In Parshas Yitro, Rashi remarks that originally all ten Dibros were stated simultaneously in a single incomprehensible syllable. They were later extracted by Moshe and individually related to Klal Yisroel.
Shehakol nihiyeh bidvaro: We exist in that one utterance, a knotted and jumbled mass where we strain to hear the strands of the divine directive amid the cacophony of colloquial existence. When we reach that clarity, when the future that beckons us becomes our present, then we will hear the harmonies resolve themselves clearly and perceive the perfect tapestry of existence as we did at kriyas yam suf.
Chazal state that this is the understanding of Shirah - the understanding of history at the point of redemption where even the worst pieces of our past are integral to our present - "Az yimalei tzchok pinu, ulshoneinu rina."