I had a "bad grade" in a class in my 4th year of undergraduate studies. 

The problem is that this class is crucial for the graduate program I intend to pursue. I got a 91%, which I know is a really good grade, but I hoped to get more since I want to do a Master's in Photonics or Electromagnetics. I think that the reason why I got this grade is that one family member passed away a week before my exam and I didn't have the energy or the will to study at that moment. 

Do you think that this grade can influence my graduate admission chances? Up to that point, I had excellent grades, and to this day I have a 95% GPA. I am aiming for selective universities.