Basically, in this movie (or show), there is a guy walking down the street. It's dark and it's rainy, and someone is getting mugged in an alley. The buy sees this and runs to help. The person thanks the guy and the guy comments on how it's a good thing he was there or something like that.
The person who got saved replies with something along the lines of "...three people walked by before you came along and saved me. They saw what was going on, but kept on walking..."

It's bugging the hell out of me! I can see it right now, but not the actor who's in it. The person who saved the mugger, more importantly does not use martial arts but rather just scares away the person.

It's not from a movie, but is from an episode of LOST. Charlie saves the day... in a flashback. The episode where he is writing down his best memories

"Lost" Greatest Hits (2007) - Plot summary (http://www.imdb.com/title/tt0998660/plotsummary)