Constant bright star-like white light, heading away with no nav or landing lights.

While watching normal air traffic on approach to phx sky harbor, we observed a bright, star-like white light heading away from us in a south east direction with no nav or landing lights whatsoever.  
My husband, who is a pilot and builds aircraft for Boeing, knew it was no commercial aircraft and only saw one single bright constant white light when looking at it through binoculars.  
Our son and his girlfriend also witnessed it and it just disappeared before our eyes with no clouds in area.  It was traveling in the oposite direction of any normal air traffic into or out of sky harbor airport, gilbert chandler regional, or falcon field nor was it high altitude.  It seemed to be at similar altitude as traffic landing at Sky harbor,but traveling in opposite direction.
Overflight of ISS at the time of the sighting.  We strongly suspect that the object was the ISS.  PD