My wife and I were sitting in the car while i filled out a paper, the car had been idle for quite awhile, and she told me the car was smoking. So I turned it off and popped the hood and then I saw green coolant leaking on the pavement on both sides of the car. It was all around inside the car, mainly in the area of the radiator itself, but it looked almost as if it had exploded. I let it cool down and looked, but couldn't find a spot the radiator blew or a hose that had blown, the place you put the coolant in was empty, so after filling it with alot of water the level finally stopped dropping, i've been driving it carefully and the level doesn't seem to alter much. Please give me advice on things to do to prevent this from happening again, also could this of caused any other damage, like to the head gausket or anything? thank you