2012 Cooper S Clutch pedal loose
 

Hello,
so i was driving the car today, took it for a 30 minute drive with no issue. As i was about to come back home i started the car and and the clutch felt weird so i restarted it and the pedal completely lost pressure. when i tried pulling the pedal back up it made a grinding noise. I checked the brake fluid, it wasn't low but it was black, no leaks under the car. I shut it off and called a tow truck and i realized that after i shut it off that the clutch pedal went rock solid.
any ideas as to what this could be? any help is appreciated!
Xavier S.