Triangle Shaped UFO that was Huge!

I was about 6 years old then. It was at a friend’s house. It was dark outside and I was on my way inside. I saw three lights in a triangle form with one big light in the center of the other three.  It was moving effortlessly and silently. It was about the size of an F-117 Stealth. But it stopped! It moved away from me and up in an "S" maneuver. And faster than anything I’ve ever seen even up to this date, it was gone.
But what really spooked me was that when my friends and I were playing tag in the dark I thought I saw one of my friends with his shirt off. But because I didn’t have my glasses on, I walked up close to him but he didn’t move until I got very close to him and then he just ran off. Then when I saw him later he had his shirt on. And when I asked about it he said he never took it off.
He had no reason to lie about it. What was it that I saw out there? Was It just him?
Witness indicates that the date of the event is approximate.  PD