The cartels rely on a thoroughly cowed populace, thus the violence against unarmed people. The cowards that carry out this violence act in the dark, under cover of night.
The cartels greatest fear is of the populace rising up against them. Armed, battle tested, American Army trained folks arrayed against them would be an absolute disaster to their operations. Cowards do not go for stand-up fights, and they likely realize that they have no chance against a trained, veteran force.
Oh, and I suggest somebody go and check that local Sherriff’s bank account for suspicious large deposits...
Way to go, militias. It is the people’s army.