During rush hour traffic this morning, a BMW 2 cars ahead of me suddenly slammed on his brakes to stop allowing a pedestrian to cross the crosswalk. This caused the car in front of me and myself to also slam on our brakes. My M3 collision avoidance alarm went off and I felt the brake pedal depress even further than had been able to press (my foot was hanging mid-air). Luckily we were all able to stop without any accident. Has anyone else experienced this where the brake pedal depresses even further than you can press down on during a sudden stop?