coolant leak at back of engine

The engine was starting to overheat so we stopped to check it out. There was water and pressure leak coming from behind the waterpump area. Couldn't see the leak but could see water spray. We got the car home, turned off the engine and noticed there was no pressure leak from front of engine anymore, but looked under the car and coolant was coming out from back of engine, in the center. filtering between the bell housing and engine. What could this be?