Live from cnn World Headquarters in atlanta, we want to welcome our viewers here in the United States and all around the world. Im george howell. And im rosemary church. Cnn newsroom starts right now. As the u. S. President ramps up his battle to stop illegal border crossings, the woman who enforced his policies is now out of a job. A source says that Homeland Security secretary Kirstjen Nielsen resigned under pressure. President trump announced her departure on twitter. Nielsen defended the white house immigration agenda, including the controversial separation of Migrant Children from their parents. President trump named kevin mcaleenan, the current customs and Border Protection commissioner, as acting secretary for the department. Nielsens resignation comes just days after the president signalled an even tougher stance on immigration. Thats right. Our Boris Sanchez had this report, recent white house decisions that took nielsen by surprise. According to a source close to Kirstjen Nie