Upper intake manifold exploded with a loud bang

I went to the gas station the other day for gas and left my car running while I went inside to pay for $10.00 in gas. When I went to go drive off I heard a loud bang then smoke came out from under the hood. My upper intake manifold exploded and I am trying to fine out if it could have caused any other damage to my engine or my lower intake manifold or if I only need to get a new upper intake manifold and gasket? My car has been running hot too, I know I have been loosing antifreeze which I do believe it is coming from my water pump. When I got in it to drive off I looked at my temperature gauge and it was not running hot. Not sure if that could have caused my upper intake manifold to explode like it did or if it could have been another reason it exploded?