Captivated is the name of the story, and captivated is what I was as I read it. The way the story cut off at the end was a shock and while I may have wanted the author to have taken it to the next stage, at least this way I can daydream the answer I want to that last statement.
One of the things that struck me as I read the story was how realistic the situation and characters were. The hesitations, the fumbling, the minor mistakes -- all done to perfection. It was also the little details that stood out, such as white-knuckled grip and the heavy breathing after a near-accident. I've been there and I knew exactly what the Tyler was feeling.

It didn't escape me that the day after Tyler said he had never punched anyone he knocked someone out, and for what was a pretty minor reason. It shows the depth of feeling that Tyler had, that he would reflexively lash out in defense of Justin, but was it a good thing for him to have done? We don't know if he had never hit anyone for moral reasons, or because he just never had a reason to. I suspect it was more the former, because there was the implication that he was harassed after Justin was outed.
The technique the author used of having the letter at the start, and then repeated at the end was also very effective. It gave the story a sense of anticipation, as the reader waited to find out what the opening meant.
I'm not sure what else to say -- a wonderful, touching tale that I hope, wish, pray has a happy ending.