Dramatic Moment

So the main character, a guy, let's call him Liam for now, is a guy on a mission for a redemption of sorts. He is normal looking teenage guy and he has been troublesome to those around him in the past. He has caused a lot of unnecessary trouble with others, combined with misunderstandings, leading to a major rift with his friends. He now knows, though an encounter with an unknowing mentor, that he has a narrow window of opportunity to make things right, but if he misses this "window", he will not have another chance, and he will have to move on, possibly advice from the friends he messed up relations with. His window of opportunity is catching his friend before she moves to another country (cheesy, I know, but I can't think of something better right now). If Liam fixes this friendship, the rift will be lessened, and they will not go their separate ways having bad memories of each other, but if Liam does not, then that is an irrevocable rift and the friend will never understand the misunderstanding.

2. The dramatic moment is Liam chasing after his friend and just missing the car with his friend in it, missing his chance to explain the misunderstanding, which may or may not need to be explained, but it may involve another friend, but not in "love-triangle" format. Liam is running, showing that he is very committed to finding his friend at this very last moment to reconcile, but he denies how futile the attempt may be and does not think of what happens if he cannot explain himself well. He isn't really concealing anything, but more information about his situation is shown gradually throughout this "scenario". The ideas that the characters are thinking throughout the film would be shown by Liam's urgency and Liam's reactions to the accusations that the minor characters are making in the past, as well as flashbacks to scenes that he was involved in. I am not sure how to reveal the subtext, but I was thinking that the film could start off with Liam running and then a person yelling after him in a rude voice "Trying to fix something? A bit late isn't it?" and he continues and turns a corner fading into a flashback to an argument with his friend that shows that they are close and not enemies but with a vague issue between them. Then maybe he runs into a person and they say "Hey!" and that leads into another flashback explaining the concept more.

3. I don't know about casting yet, but the setting would be school, so I think that would be the most logical place to have the leaving scene, for there would be people around who would know the situation going on because it is a high school campus and everyone is into other people's business and it is a reasonably logical place for a friend to leave such a place for the last time before moving, next to their house or the airport. I don't know much about the production design yet, but I thought that there would be a lot of good opportunities to have continuing action throughout the scenes switching to make good transitions. Also, the school has a lot of good twist and turns for a "chase" of sorts (its just him trying to get to the one point as fast as possible).