In recent weeks, a group calling themselves the United Constitutional Patriots illegally detained hundreds of immigrants at gunpoint in a remote part of the border near Sunland Park, N.M., and turned them over to U.S. Border Patrol.

The group posted videos online showing men, women and children — some too young to walk — kneeling and sitting in the sand in the dead of night, surrounded by masked men in military camouflage. The men carry rifles and, in some cases, military-style weapons. In one of UCP’s videos, a vigilante shines a flashlight on two immigrant men lying in the dirt and muses, “The only problem is if we shoot on the hill it will be an international crisis … It would save some time though, wouldn’t it?

The situation is a disaster waiting to happen. Any wrong move, any unexpected turn could cause the men to fire on the families. Imagine one of the immigrants drawing a cellphone from his pocket that the vigilantes mistake for a weapon. Even highly-trained police officers sometimes fail to react appropriately in such situations. And many of the vigilantes carry weapons that are designed to deliver death widely and quickly.

Last week, federal prosecutors charged the leader of UCP, Larry Mitchell Hopkins, with unlawful possession of a firearm from events dating back to 2017. That is not enough. Video evidence strongly indicates that UCP members are wantonly violating state and federal laws against impersonating an officer, assault, false imprisonment and kidnapping. Many of the vigilantes wear official-looking badges. In several videos, they can be seen announcing themselves as “United States Border Patrol” or as “policía” to the immigrants.

The vigilantes claim they are simply conducting “citizens’ arrests.” They are wrong. New Mexico courts only allow that authority under narrow circumstances. Just as no law empowers private citizens to pose as FBI and arrest people at gunpoint for suspected drug crimes, so there is no law that empowers civilians to form private militias to enforce immigration laws. We call that vigilantism.

From the KKK to Kristallnacht, history is littered with examples of where those activities lead. And like those examples, racism clearly is a motivating factor. In one video, a vigilante likens the immigrants to “roaches.”Last week, Union Pacific railroad and Sunland Park police removed the vigilantes from public land, but we have received reports that the UCP is re-establishing their camp on private property and threatens to resume their vigilantism.

To our knowledge, no government authority has ordered them to stop illegally detaining immigrant families or impersonating federal officers. Indeed, a U.S. Border Patrol spokesman was quoted last week acknowledging that — despite clear videotape evidence of criminal activity — the agency will not even investigate the UCP unless it receives a complaint from one of the detained immigrants. That amounts to complicity in this dangerous behavior.

Last Friday, Sens Tom Udall, D-N.M., and Martin Heinrich, D-N.M., called upon authorities to immediately investigate the UCP. The ACLU adds our voice to theirs. Law enforcement needs to step in and stop this debacle now. We do not contest UCP’s right to organize themselves and observe goings-on along the border. But we do want to prevent a humanitarian disaster. Immigration enforcement belongs in the hands of trained, authorized professionals — not in the hands of armed vigilantes.

This op-ed was originally published in the Santa Fe New Mexican.