A rifle bullet kills an animal by destroying tissue, disrupting the function of vital organs or the central nervous system, causing blood loss, and perhaps by shock to the animal
Crossbows are occasionally used in learn-to-hunt programs. A broadhead kills by hemorrhage rather than shock. Its razor-sharp edge cuts the veins and arteries along it path, which can cause extreme hemorrhaging if vital areas are hit. The hemorrhaging results in loss of oxygen to the brain and death occurs.
Death can occur within seconds, from a well placed arrow. However, even though death is rapid, the deer is still likely to run after being hit and will have to be recovered by following its blood trail.
Even if bows or crossbows are not used in your program, we recommend that a brief discussion between the differences between a deer killed by a firearm and one killed by a broadhead. Both can result in quick, humane kills.