1991 Mazda Miata radiator fluid leak

I just bought a 1991 mazda miata mx5, with 189000 miles on it. I drove home, then went back to the dealership where I purchased it to get my other vehicle, when I drove home again, the car lagging when I pressed the gas. I then noticed the temperature guage rising really fast, so I pulled over and could here a boiling sound coming from the front of the car. I popped the hood, and saw that radiator fluid was spilling all over the ground. I thought I had bursted a line in the bottom, but upon further inspection it seemed the hose was fine. The leak finally stopped as the engined cooled from being off. What could be the culprit?