1x1 - The Walking Dead - Webisodes

The web series tells the origin story of Hannah, also known as "Bicycle Girl", the walker whom Rick Grimes killed in the first episode.[1] Rick risks a walker encounter to go back and find Hannah before he sets out for Atlanta. After telling her he is "sorry this happened to you," Rick shoots her in what is clearly a humanitarian gesture, which reveals much about Rick's own character and sets a tone for the rest of season one.