In the opening pre-title sequence, when attacked by the monster dropping your weapon in hand and running like a terrified ferret, like Arthur does, is not the action of either a trained warrior OR a trained hunter. Retreat can certainly be an option, but to drop his obvious defense or counter-attack, the spear, is just not something that should have been done. And being startled by your supposed prey is not an excuse. It's one of the things training prevents. As a matter of fact, the most likely response of a trained warrior is to jab at the monster's eyes or into its mouth.