1994 Lumina APV Brakes Problem

Hi Guys
I'm new to this forum.
Today I was driving 1994 Lumina APV and when I stopped and pressed brakes a bit to hard than usual I heard a pop and after that an exclamation mark came up on display and P in red. Brakes now hardly work. I press all the way in and they hardly stop a car and it feels very very light. Can anyone please help me out what's wrong with them?

Thanks

Sounds like you blew a brake line. Which means you are now probably only using two brakes out of your 4. Better not drive it until you find out what's broken.
I've had it happen on several vehicles. The lines eventually corrode and then one day - POW foot to the floor.