Conservationists conducting a bat population survey in Arizona filed a police report last week after they were ambushed by three armed militia members who mistook them for border crossers or smugglers, Tucson News Now first reported. The night-time encounter near a popular camping area, comes at a time when the number of armed vigilantes purporting to guard the border has grown in response to an increase of migrant child arrivals arriving at the southern U.S. border.

Three armed and camouflaged militia members were on their ATVs when they shouted in Spanish and put a spotlight on a group of conservationists walking back to their campsite. The conservationists had just come from counting bats in a local cave around 11pm in Sonoita, Arizona, about 31 miles from the U.S.-Mexico border. One researcher told the Huffington Post, “We didn’t know what they were doing. We started hiding behind rocks. We’re not doing what they’re saying, and they’re acting kind of jumpy. … We had them yelling at us with spotlights, acting like they have some kind of authority.” The deputy’s report stated that the scientists identified themselves and continued to walk to their campsite, “while seeking cover.”

Santa Cruz County Sheriff Tony Estrada told Tucson News Now that a militia member apologized afterwards, but that the conservationists “weren’t very receptive about the apology.” Estrada condemned the group saying that they could “get in the way and they could get hurt. Or they could hurt somebody else.” He added that the county “does not welcome border militia groups.”

More: Armed Militia Members Ambush Conservationists, Mistaking Them for Border Crossers