You can see the details about the shooting in the wikipedia page -
BART Police shooting of Oscar Grant - Wikipedia, the free encyclopedia
I vaguely remember reading about it a couple of years ago.
I'm hoping Chad plays
Johannes Mehserle - The cop who shot Grant. It would be a more difficult and interesting role to tackle instead of the cop's partner. Plus, I'm a HUGE fan of Octavia Spencer!
This movie is going to be fantastic!