It builds suspense because it looks like they’re having a friendly talk because the way they’re looking eye to eye but really they’re not having a friendly talk.Tom Chaney killed Mattie’s dad.Tom is about to kill Mattie but Mattie kills Chaney. We.We didn’t know that was going to happen.In Homicide you killed someone and you get caught so because you said “it was self-defence he just came at me” So you admit  you killed someone so you are going to serve the consequences.