Federal officers carrying out President Donald Trump's immigration crackdown often use harsh methods to scare or repel those they see as getting in their way. Hundreds have been hurt, and courts in at least four states have found that officers used force inappropriately and indiscriminately.

NBC News reviewed dozens of incidents since the spring and found that Department of Homeland Security officers have repeatedly deployed "less lethal" weapons in ways that appear to violate their own policies or general policing guidelines.