Hundreds around the country look for training in how to respond to immigration enforcement

The shriek of whistles and a cacophony of cars honking have taken on new meaning on the streets of major U.S. cities in recent months — a warning to all those in earshot that immigration enforcement is nearby.

The warning tactics from activists have become popular in cities recently targeted by Border Patrol immigration operations. In Los Angeles, Chicago and Charlotte, North Carolina, residents protested immigration enforcement actions and began coordinating street patrols, organizing neighborhood watch groups and recording videos of both immigration officers apprehending people and agents carrying out operations largely while masked and in unmarked vehicles.

Community activists have denounced what they say are increasingly aggressive tactics by immigration agents as residents patro