I do think you need to have a conversation with him. The first thing I would do, is shake the chip off your own shoulder. Give him the benefit of the doubt that he really is trying to make life easier for you. Go in to the conversation with that assumption. Think how much more pleasant the conversation becomes when you do so.
I would say something along these lines: I really appreciate that you were being helpful in ordering supplies for the office break room, however, since i am responsible for the budget for that department, you can understand that I need to stay aware of all changes in vendors. Going forward, I'd like to have a conversation on these kinds of things so that we aren't duplicating our efforts. After all, we all want the company to succeed.
Marie
