Auto Insurance Claims: At fault, side fender, double parked

Question
A car was douple parked (with its brake lights on) 4 cars in front of
a street parking spot (actually it was a spot large enough for two
cars), So I waited momentarily to see what the driver's intentions
were and whether or not I should go around or if I could park there,
I signaled and pulled forward into the spot (no need to paralel park
as it was a huge spot); as I was straightening out my car I saw this
car that was 4 spots in front of me and double parked go into
reverse. Immediately I blew my horn, as I could not move my car
anywhere. The driver dented and scraped the driver's side fender
above the wheel, and his car has some scrapes on the back
bumper. Who is at fault?

Answer
Based on what you have described and if you had full possession of that spot and were stopped when you were hit as you stated you had nowhere to go, then the other driver is definitely at fault for hitting a parked object.  If you were moving then honking your horn and the other precautions you stated would not make you at fault.  I would need more info to give you a more solid answer.