The short sentences and the punctuation affect the tone of the excerpt by creating a sense of urgency, tension, and suspense. The short sentences are often incomplete or fragmented, which suggests that the narrator is in a hurry or under stress. The punctuation, such as the dashes, commas, and exclamation points, also indicate that the narrator is speaking rapidly, breathlessly, or emotionally. The tone of the excerpt is one of fear, anxiety, and excitement.