The fight occurred just after the race. According to USA Today, driver Brad Keselowski's broken car slowed considerably on the final lap of the Kobalt 400 at Las Vegas Motor Speedway. Busch made a move around Keselowski, putting him in Logano's racing line. Logano didn't back off, eventually making contact and causing Busch to spin. Logano finished fourth while Busch finished 22nd, the last driver still on the lead lap.
Busch confronted Logano immediately following the race. The video from Fox Sports shows Logano's crew pulling Busch off Logano. While Logano was unhurt, Busch was left with a sizable gash in his forehead. There has been no comment from Nascar, but penalties could be handed out sometime this week.