mayorkas witnessed today. >> if you come to the united states illegally, you will be returned. your journey will not succeed and you will be endangering your life and your family's lives. >> right now we're going down to the international bridge here in del rio. >> reporter: cnn rode along with lieutenant christopher olivares. >> right now we're here at the area -- this is the main area they're crossing. >> reporter: an area where from the air, cnn cameras captured migrants crossing freely just days earlier. >> they were crossing to and from the u.s. via this dam. just take a look. that's mexico. you can see the flag flying. >> reporter: and now, the flow has stopped. oifleras says this sea of texas state troopers helps secure the river. and moments later we see the shocking scene under the del rio international bridge. thousands of migrants, mostly haitians, say officials, living in squalor like james who says he left his home country for