(I could not find the same question. If this has been asked before please let me know.)
I wrote an e-mail to a professor to be his student and he responded with his area of interests. Then I wrote for further information but he did not respond for couple of days. So I contacted another advisor and we agreed to work together.
Few hours later the first advisor replied saying he could give me something to work.
How can I let him know that I agreed to work with another professor? Did I do a mistake by not waiting more for his response and contacting other advisor? Thank you.