article: "Mum, did you hear anything? I, uh. I thought I saw an alien."
  "Are you all right? Just a dream ! "Mum answered.
  Then I went back to my room. As I walked to the window, I cried, I saw a little alien, no more than three feet tall, with big and black eyes. It tried to run between my legs and escape through the window. Although I was scared, for some reason, I squeezed   my legs together in time to catch it. It took out something and hurt me. I felt a terrible sense of nothingness and fainted  . Then I woke up.
  At first, I could hardly move. I wasn't sure whether it was a dream or not. I pulled myself out of the bed and walked downstairs. I saw my mum in the kitchen. She was really getting my brother ready for school, wearing her pink clothes. Then I realized it was just a dream because in my dream she was wearing her work clothes.
  From then on, I always dreamt about aliens and all the dreams felt so real. At that time, I really thought maybe I had some kind of relationship with aliens. About two months later, I stopped having such dreams. Later I realized that l used to have those dreams because I always read books or watched TV programs about aliens before I fell asleep!
question: The writer found that it was just a dream   _  .
options: as soon as he woke up before he went downstairs when he saw his mother when he was hurt by the alien