Brutal grind/knocking feeling and sound from braking hard?

A while ago, I was coming off the freeway and I needed to brake hard to come to a stop. At the time I was going about 30mph and turning about 45 degrees. When the brake pedal almost reached the bottom of the floor(the last few cm's you can push it), the pedal began to chug/knock/vibrate or w/e u call it violently like there were rocks in the way preventing me to press down harder smoothly and it felt like it prevented me from braking like the pads had no pressure on the rotors. It also didn't sound so great when it happened.

Today, I tried braking hard again on a straight road at about 15mph and it just felt and sounded like something screeched. It doesn't have the smooth feeling as the pads hit the rotors like it normally does during normal braking.

Thanks for reading this, pads don't seem to be worn so I don't know what is causing this. And since the first incident wasn't just the screech feeling, I suppose it shouldn't be the worn pads problem.