WE WERE IN A COLLISION. A VEHICLE REAR ENDED US HARD AROUND 50 MPH ESTIMATE. WHEN WE WERE HIT THE PASSENGER SEAT FOLDED AND THE PASSENGER HIT THE HEADREST AND THE HEADREST FLEW BACK TO HIT MY REAR PASSENGER IN THE FACE. OUR VEHICLE WAS AT A COMPLETE STOP ON A HIGHWAY. THE OTHER VEHICLE HIT US ON THE PASSENGER SIDE STRAIGHT ON.