Angry with neighbour for banging against the ceiling?

So, I recently moved into a new apartment. Yesterday I was playing my digital piano. I was wearing headphones, but the action of the keys still makes some noise, which I guess tranfers down into the apartment below me. Now, at some point I suddenly heard my downstairs neighbour banging against the ceiling loudly (and I felt it through the floor). After pausing for a bit and starting again, the banging continued. I do not make much noise generally and have never had problems with any neighbours before. This while my downstairs neighbour regularly plays relatively loud music until late at night. Right away I went down and inquired in a friendly manner, but he still seemed rather annoyed with me. I feel that it's a pretty aggressive way of communicating from his side and that it may cause some problems in the future if he keeps communicating broom-to-ceiling instead of human-to-human.

Is it normal that I'm angry about him banging against the ceiling instead of just coming over to tell me in person? I should note that I do not have any previous history with him apart from introducing myself. I also believe I am not a scary person :p