Trail leaving object stops in mid-air then vanishes in a puff of smoke, the smoke and trail vanish immediately afterwards

I was driving on the Pont Champlain Bridge from Ottawa, Ontario, towards Gatineau, Quebec.  The time was 18:23 on August 18, 2013.  The sky was crisp clear daylight. While waiting in traffic  I noticed a growing trail moving away from the left of the sun which was North-West of the direction my vehicle was heading.  Initially, it seemed like a trail from a normal jet engine, yet I could not see a jet or other object from which the trail was coming from.  The speed was moderate and consistent.  The trail was not such that it remained visible the whole traveled distance (such that you could follow the whole path the object had taken).
I continued watching the moving trail for about 15-30 seconds when I saw the most interesting thing ever: whatever the object that was causing the trail ceased to move at once and all of a sudden it vanished with a big puff of smoke that disappeared right behind it.  Even more interesting, the trail vanished almost instantly and there was no sign of anything. It was almost like a “puff” of smoke and gone.  Shortly after (like 10 seconds), I notice a plane heading in that direction.
This was a sighting of one object too small that I cannot describe a colour or shape for. It could also be that the sun was just hitting my eye so I could not see the object.  But the trail it was leaving and everything else that happened were very very clear to me.
Witness elects to remain totally anonymous; provides no contact information.  PD