Set up: You recently discover three things.
One, someone is changing Reality in ways that are subtle, though occasionally something happens that implies whoever is doing this is holding back, and has more power than they are displaying.
Two, that you are immune from being directly affected by these changes. The world around you might change, but you retain your memories and you are 100% certain that nothing about you personally has changed. Note that, for example, if this person turns a friendly dog into a large, angry Brown Bear, you best move away quickly.
Three, that you figured out who is doing it and that it is someone in your own community.
Assuming that this person likes playing with this power enough not to listen to reason and that there is a risk that taking the wrong action might escalate things, how do you stop a Reality Warper?
Bonus: If you are in physical contact with something, that something also doesn't change (example: If you are driving a car, the car doesn't suddenly turn into a boat)