Sorry to hear that...I know how you feel, I've been in the same situation before a few years back. but even if you were already a doctor and had the knowledge necessary to save the man's life, you might not have had the necessary equipment. for example, if the man needed to be intubated, but you didn't have an intubation kit at hand, how much more can you do?
obviously, this can only be determined on a case-by-case basis...but the main thing is as a physician, you do what you can with what you got, and you shouldn't burden yourself with the what-if's -- everything happens for a reason.
but like jiggerdigger mentioned, you can use this experience as inspiration while going down the long road of becoming a physician. for me, i can credit the experience i had with my interest in emergency medicine.
btw...hope you get into western! with how much you wanna go there, you deserve to get one of their spots.