Group of friends an I follow a UFO on bicycles, I have a sighting alone about a week later.

I was about 8 years old and a group of kids in my neighborhood were riding bikes on Longfellow Ave. I looked up at the sky and noticed a UFO approx 500 feet above us, silently, we all decided to follow it and we rode our bikes all the way to the end of the street and then turned around when it sped up to the point where we could not keep up. Approximately a week later, at approximately 5pm, I arrived back  home from a Brownie Troop meeting (my mom picked me up and drove me to the house afterwards) and my mom brought my brother in the house to start dinner. For some reason, I decided to not go in the house right away, I was on the side of the house and looked up and could not believe my eyes, I saw the same UFO I saw a week earlier, I looked up and felt paralyzed and did not move for what seemed to be approx 10-30 minutes (it was hard to tell how long it was there).  The disk had square windows that beamed white light, it was silent and quite mesmerizing. When! it left it, darted up at the sky and seemed to silently disappear at an unbelivable speed.  My mom asked me why it took so long for me to come back in the house because she was almost finished making dinner.  I didn't say anything about the UFO to her because I thought she might not believe it, anyway.
Witness indicates that the date of the sighting is approximate.  PD