The deer shown in the series are White-tailed Deer, which live throughout the state of Florida. Key Deer and Sambar Deer are confined to islands.
(Flashback) While they were preparing to hunt pheasants, teenage Dexter asked Harry if he had ever killed a person, and what it felt like to do so. After a short discussion on the topic, Harry decided they would hunt something bigger than a pheasant that day. Later, near a forest edge, Dexter watched Harry shoot a deer, but it remained alive. Harry then pulled out a knife, saying to Dexter, “For now, this is how we’ll control the urges you feel.” Dexter readily took the knife and stabbed the deer.
Arthur Mitchell asked Dexter to accompany him into the woodlands on the next morning. After they arrived at the destination, Dexter learned they were going to cut down a tree for “better lumber.” While there, Dexter had a chance to kill Arthur with a chain saw -- but he didn’t. On the way out of the woods, Arthur struck a deer with his van and was horrified. The deer, lying in the road, was not quite dead. When Dexter told Arthur to kill it to end its suffering, Arthur was unable to do it. This mystified Dexter, since he knew that Arthur ruthlessly killed people. Dexter then took the ax, tempted to use it on Arthur. However, Dexter passed up another opportunity to kill Arthur. Instead, he swung the ax downward, swiftly killing the deer.