Extensive car search no reasons given

My fiancee and I took a week long vacation to Mpumalanga , We then decided to go to the Kruger National Park on the 3rd of April 2016. So we driving around admiring nature like the other tourists then suddenly a helicopter flew over us several times then it disappeared. At the end of the day driving towards the Numbi Gate after the game drive,lunch, and shopping as we were about to drive out we were stopped by guards. Our whole car was searched....the boot, the bonnet, under our seats,the spare wheel compartment,under the car, and our bags!!!!!! It was a humiliating experience...surprisingly enough the cars before us and after us were let out no questions asked no searches. We felt like suspects of the unknown crime! The guards would not tell us what the problem was. It was a very disgusting behavior! If that is their standard procedure when it comes to security then its disgusting.I want to know why we were treated in that manner. Does this kind of behavior apply towards South Africans only because everybody else was foreign. Family and friends will know not to set foot there!