1/21 The Flag

Today I woke up early when I drink a cup of green tea, I look outside from the window. The sky is still clean, but today is a windy day. I looked at the birds flying in the sky. I looked at the flag on the Alameda County Court House. It was down to the half on the flagstaff, and the flag on an other building looked the same. So, I don't know what the story is about the flag because in my country, if an important person dies, the flag will be down to the half on the flagstaff. I don't know American culture too much, but I want to understand this, so dear teacher, could you tell me?