Video of a TSA Pat Down AFTER Mother and Sons Get Off Train

This is so mind boggling to me! I am still trying to figure out within WHAT law or right would the TSA have to pat down people AFTER they got OFF a train in Savannah, Ga.?

Where is the sense in patting down people when they have gotten to their destination?

But, more importantly what RIGHT OR LAW allows TSA to pat down people riding on trains?

If all of this is true, then we are so down the rabbit hole in being a POLICE STATE in the United States! All of this invasion of privacy and having to SUBMIT to other people feeling us up all in the name of keeping us “safe from terrorism”?