Also it is worth saying that an employee coming to a manager / founder / owner to report a problem "in confidence" is not the same as you not being able to do a

Also it is worth saying that an employee coming to a manager / founder / owner to report a problem "in confidence" is not the same as you not being able to do anything about it. You need to manage that person as well so that they know that they've a) done the right thing b) aren't at fault for whatever the consequences are and c) that you / the company do care about them. Even if you weren't to fire the person (and as a brand new hire firing seems a better option) then you would need to provide specifics when having the conversations that would follow. Mainly because all you have so far is an allegation, making your mind up (not the same as considering options) beforehand is not good. Regardless of whether you fire the employee or not the key thing is to prepare for the conversation. If you're a founder speak to your co-founder(s), if you're a manager don't just speak with HR and have them in the room for the meeting but prepare with them. Have your opening statement well rehearsed, consider different conversational flows and how you might react to them. This isn't a thing to do on the fly.