I was slowing down in a parking lot to park. I applied the brake and the pedal was very stiff and the vehicle wound not stop. I finally stood on the pedal and it acted as though the antilock activated and started shuttering. It finally stopped without damage. A warning of service brake assist displayed on the dash. This began to happen about 3 months ago intermittently, but now is a more frequent action. I have not taken it to the dealer and thought of replacing the brake vacuum pump but don’t know what to do. Any assistance you can provide will be greatly appreciated. Thank you and have a great day! [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)