Here's an article that debunks many of the reports of snipers shooting at rescue personnel, and most of the rest of them have yet to be substantiated...

http://www.realcities.com/mld/krwashington/12801034.htm

I got the information in my previous post from seeing interviews of people who were there at the time, stranded on rooftops waiting to be rescued. They said they did not witness anyone shooting at rescue personnel, but they did see people shooting in the air in order to alert rescue personnel to their presence and their need to be rescued.