Scene at the Maris' house

Every time I watch the scene where Barry Pepper and the girl who plays his daughter are in the backyard barbequeing, before the phone call threatening the children, we see the barbeque lid fall on the little girl's fingers. Barry reacts quickly asking if she's okay and blows on her fingers. From the look on the little girl's face, it didn't appear to be part of the scene. The poor girl looked really shocked. I couldn't find anything in trivia on this scene so I was wondering if anybody knew if it was something spontaneous that they caught on film and put in the movie? It just really doesn't make sense as a planned scene because we already know Roger Maris loved his children. It makes more sense that the cover falling on the girl's fingers was an accident and Barry Pepper reacted, they caught it on film and decided to use it.