An intensely bright strobing light that appeared, silent, and moved with incredible speed across the sky changing position.

On the evening of July 31st,  2014, at approximately 10:30pm, I was driving on route 15 north of Woodside, Delaware, midway between Woodside and Camden, Delaware.  It was a clear starlit night.  
All of a sudden I saw an intense strobing light, emerald green/bluish in color.  The frequency of the strobe was once every couple of seconds.  The strangest thing to me about this sighting is that at no point could I see an object, nor was there any sound associated with it.  It was as if there was a haze surrounding the area where the light emanated from  and it was as if the light came from nothing but open air.   
When I initially saw the strobing light, it was directly in front of me.  The distance was difficult to determine but my estimate was possibly less than a half mile and probably less than 1000 feet high.  The flashing light was so bright that I couldn’t  see the object itself, but it traveled at an incredible distance in an instant and changed direction several times.  It was almost as if it was following me. 
I stopped my vehicle to watch the object.  As I sat on the side of the road  the object came back toward my direction and slowly descended below the tree line into the field.  At this point the light stayed lit so it was visible to me as it descended.  Even though the light was visible no object could be seen, just the intense and now steady bright light.  
Once again the distance was difficult to determine because of darkness but it appeared to be less than a half mile away based on the distance of the trees that I could see.  
The light ceased to flash after approximately thirty seconds or so.  
I called my grandson who was at my house at the time of the incident and told him what was happening as it happened and stayed on the phone with him during the entire incident.  Much to my dismay I am not proficient with the use of my cell phone camera and was unable to capture any of this sighting.  
The entire incident lasted approximately 5 minutes.  I had to ask myself, “What did I just see?   Did I really see what I was seeing?  What did I see?  How do I tell someone that I just saw something but there was nothing there, just a light coming out of nowhere that moved across the sky at incredible speed.  If I tell anyone of this, they’ll never believe me”. 
I called 911 when I got home just a few minutes later to report it in case anyone else witnessed it.  I also called the Dover AFB air traffic control tower at the air base and left a message about the incident but they never responded or replied to my call.  
There were very few cars on the road in this country area.  The 911 dispatcher whom I spoke with gave me the number to the National UFO Reporting Center.  They instructed me to immediately write the events of the incident down and file a report while it was fresh in my head, which I did.
((ADDENDUM FROM WITNESS))
Mr. Davenport,
I made some amendments t my report of which I had saved.  I'm including it in the attachment to this email for you.  I'm sending it to you so you can read it and have if immediately and I will now resend the report you requested,
 
Thank you so much!  I still can't believe what I saw nor can I explain it clearly enough to ever make anyone understand what I saw.
 
((name deleted))
U.S. Army Retired
((END ADDENDUM))
We spoke via telephone with the witness, and he sounded to us to be quite sincere and sober-minded.  We suspect that he is a very good witness.  PD