I didn’t know your story it’s just for your reference.
The 2 native ratsnakes (Ptyas korros and P. mucosus) are actually not ratsnakes. They don’t belong to the ratsnake genus. They still eat rats but they favorites are frogs and toads.
If you find snakes in an urban area, even in parks, that could be something not native. I’ve seen many times of snake escape and also snake release.