Not sure about US laws, but in my country, even if you “only” hit an animal you HAVE to report it, either to the police or the “local hunter community”. and yeah, my dad works for insurance and he told me about the damage a deer or a buck can do to a vehicle. many vehicles were wrecked after that.
Calling authorities to report a car vs deer isn’t that uncommon in South Dakota. If he was driving a State issued vehicle he has to report it. If it was a personal vehicle and had enough damage that would require it to be repaired no body shop in the state will repair it with out a red tag which is only issued.