Circular Object hovering above the Allegheny River in the Spring of 1968

While driving down Hwy 28 from New Kensington to Springdale, my Mother shrieked in Horror and stopped the car along with dozens of other drivers to observe a huge circular object hovering to our left, just feet above the Allegheny River.
We stopped the car along with everyone else and got out to observe this Object.  It had a Glass Dome on top, flashing lights underneath and stationary lights on the side.  It was approximately 200 to 300 feet in diameter.  I remember, as well as my two other sisters in the car, that the object almost took up the whole width of the river!  It was Pulsing and making a Humming/pulsing sound.
While the 4 of us were watching, it started to pulsate, with the lights moving around the sides faster and faster.  It was then pulsing and flashing SO fast that we thought it was going to Explode!  We screamed and jumped back into the car.
So did a lot of other people!  All of a sudden there was a bright Flash with thousands of points of light expanding and falling onto the river, almost like a 4th of July sparkler.
The next thing we realized was that the Object had either EXPLODED or had DISAPPEARED!  On the way home, we all were crying hysterically with my Mother almost rear ending the car in front of us.  As soon as we hit the door, my oldest sister called the Police Station to report the sighting.  The police told her that their switchboard was lighting up w/ calls from all over the county of sightings of this UFO.
I will never, ever forget this day!  To this day, we STILL talk about seeing this UFO pulsate and disintegrate above the Allegheny River that Spring of 1968!