evidence: President Trump has directed U.S. Immigration and Customs Enforcement agents to conduct a mass roundup of migrant families that have received deportation orders, an operation that is likely to begin with predawn raids in major U.S. cities on Sunday, according to three U.S. officials with knowledge of the plans. [...] Large-scale immigration enforcement operations are typically kept secret to avoid tipping off targets, but Trump’s tweet Monday blew the cover off the roundup. That the operation was revealed publicly stunned law enforcement officials, and they believe it gave them more latitude to discuss the raids. [...] The expedited family court docket, or "rocket docket," was developed by Trump officials late last year in an effort to deport more migrant families with the belief that a highly visible roundup operation could have a deterrent effect on others in Central America considering the journey.