Texas Law Enforcement Warns People Against Carrying on Their Own Property

This Reuters article is about the increasing number of "militia" showing up at the Texas-Mexico border to try and dissuade illegals crossing. However, there is this bit:

Some say it is just a matter of time before one of these groups sparks a deadly firefight along the border. 

Eddie Guerra, sheriff of the Texas border county of Hidalgo, is concerned. 

"When there are situations with any individual who is bearing arms in public or on private property, there is always a concern amongst law enforcement of possible misidentification that can lead to friendly-fire tragedies," he said. 

Border Patrol has warned the groups that taking matters into their own hands could have "disastrous personal and public safety consequences."

The story notes, though, that "[t]he only live fire they [i.e., the citizen volunteers] have seen has come from a Border Patrol agent who fired at them."

This comes across, at least to me, more as a threat than a caution. Besides, as the persons intruding on private property, it seems to me that it is law enforcement's responsibility to take extra caution--after all, it is they who are the trespassers, not the citizen volunteers.