Thank you everyone for your posts. My heart is still racing and I haven't settled down yet. I am sure Drake thinks I am nuts!! He has so much fun when he at the park off leash and I love seeing him be himself. He explores and sniffs and romps around!! He is so happy out there. He has never left our site before. Today was a very first. I am still trying to decide what is going to happen next time.

Don't know if this is a real "problem" or not -
but you might want to check with the "local authorities" to see
if there are any laws about domestic dogs "chasing" wildlife such as deer.
Allowing him to run free in a "nature park" might be a no-no. ??

He might never "catch" an alert and healthy deer;
but a fawn or an older one might not be so lucky.
And if the Draker isn't carrying his hunting license - !
Dogs here in Germany do not have to be leashed. Even in the city. You see dogs walking around behind or infront of their owners leashless!! All the dogs at the park walk around free without a leash. As for hunting, it is not allowed on the park grounds!