Sudden Irrational Fear

Tonight I was vacuuming the floor, which I have done on several occasions in the past, and to my surprise - Orion screamed in shear utter horror when I turned it on! He was terrified! So I hurried and vacuumed the upstairs and he screamed bloody murder every time I even looked in his direction! I had a hard time calming him down afterwards, snot and all!