Death and Mourning

Shalom, I am a Kohen. After Shabbat I went to visit a neighbor’s house for the first time. While I was there I noticed a cabinet with photos of a woman and a card with her name, photo and year of birth and death. I walked right by it to the dining room. At the time I thought absolutely nothing of it. There were so many other things on my mind and it passed my innocent mind. Later I overheard another friend of mine being told to stop bouncing a ball in the residence. He was told: “Oh you shouldn’t bounce balls nearby the altar!” It became clear to me that cabinet with the photos was turned into a type of altar and shrine to her. This seems wrong to me. Especially as a Kohen. I have never had this happen to me and I had no clue what to do. I want to do the right thing and not lie to myself or turn a blind eye. Rabbi, how should I view this situation?