The case that inspired the new movie "Fruitvale Station"

Years before Trayvon Martin crossed paths with George Zimmerman, the killing of Oscar Grant made national headlines, and triggered protests across the country. Grant's story is the subject of the new movie "Fruitvale Station."   Unlike the Martin case, there were plenty of witnesses to Grant's death, and many recorded it with their cell phone cameras. We want to warn you it may be difficult to watch.   CNN's Kyung Lah looks at what happened.