Break Failure on 91 300e 4matic

While parking my car, I felt something give, the brake pedal went to the floor. What broke??

I drove cautiously home, and here are the symptoms,

first few mm of movement of brake pedal, brakes seem to response as normal, but if you push farther, the brakes bite harder, then give and there's hardly any pressure to slow the car, and the pedal goes to the floor, pumping does not seem to rectify the situation,

I read some of the history posts on brake failure, but my symptoms don't seem to match those other threads.

brake fluid is at the correct levels,and clearish, not a dirty yellow,

all advice welcome.

PS, I put new pads all around recently, (2000 miles ago)