Mexican criminal organizations known as cartels are using drones to carry out violent attacks on the public and rival gangs south of the border, according to a former U.S. Border Patrol official.

Carl Landrum, retired chief of the Border Patrol’s Laredo, Texas, region who now works for counterdrone defense company Dedrone, testified before House lawmakers Tuesday afternoon that “dozens and dozens” of violent incidents in Mexico have been facilitated through the unmanned aerial systems.