Did you know the Texas Rangers massacred 15 mexican people in Texas in 1918? Here is an article from Wikipedia. This excerpt is from the "Texas Ranger" page.

The Mexican Revolution that began in 1910 against President Porfirio Díaz changed the relatively peaceful state of affairs along the border drastically. Soon after, violence on both sides of the frontier escalated as bands of Mexicans took over Mexican border towns and began crossing the Rio Grande on a near-daily basis. Taking over trade routes in Mexico by establishing themselves as road agents, Mexican banditos turned towards attacking the American communities for kidnapping, extortion, and supplies. As Mexican law enforcement disintegrated with the collapse of the Diaz regime, these gangs grouped themselves under the various caudillos on both sides of the border and took sides in the civil war most simply to take advantage of the turmoil to loot.[13] Then, as the lack of American military forces for defending the border was made more abundantly clear, the scope of the activities soon turned to outright genocide with the intention of driving Americans out of the Southwest entirely and became known as the Plan de San Diego in 1915. In several well rehearsed attacks, Mexicans rose up and in conjunction with raiding Mexican guerrillas among the Villistas within weeks killed over 500 Texan women, children, and men.[14]

The political decision of the Texans was clear: restore control and order by any necessary means. As Governor Oscar Branch Colquitt instructed Ranger Capt. John R. Hughes: ...you and your men are to keep Mexican raiders off of Texas territory if possible, and if they invade the State let them understand they do so at the risk of their lives.[15] Hundreds of new special Rangers were appointed by order of the state, which neglected to carefully screen aspiring members. Rather than conduct themselves as law enforcement officers, many of these groups acted more like vigilante squads. Reports of Rangers abusing their authority and breaking the law themselves became numerous.[16] The situation grew even more dramatic when on March 9, 1916, Pancho Villa led 1,500 Mexican raiders in a cross-border attack against Columbus, New Mexico, increasing the high tension that had already existed between the communities.

The final straw that broke the camel's back was the killing of innocent villagers wrongly accused of raiding the Brite Ranch Store on Christmas Day in 1917. On January 1918 a heavily armed group of Texas Rangers, ranchmen and members a troop of U.S. Cavalry descended upon the tiny community of Porvenir, Texas on the Mexican border in western Presidio County. The Texas Rangers and company rounded up the inhabitants of the village and searched their homes. The vigilantes then proceeded to gather all the men in Provenir ( fifteen Mexican men and boys ranging in age from 72 to 16 years) were marched off into the cold and bitter darkness. A short distance from Porvenir, the innocent men were lined up against a rock bluff and shot to death. The innocent men were Manuel Morales, 47, who possessed a deed to 1,600 acres (6.5 km²), Roman Nieves, 48, who possessed a deed to 320 acres (1.3 km²), Longino Flores, 44, Alberto Garcia, 35, Eutimio Gonzales, 37, Macedonio Huertas, 30, Tiburcio Jaques, 50, Ambrosio Hernandez, 21, Antonio Castanedo, 72, Pedro Herrera, 25, Viviano Herrera, 23, Severiano Herrera, 18, Pedro Jimenez, 27, Serapio Jimenez, 25, and Juan Jimenez – the youngest victim at age 16. In January 1919, the Porvenir massacre came under the scrutiny of the Texas House and Senate Investigation of the State Ranger Force.

Before the decade was over, thousands of lives were lost, counting Texans and Mexicans alike; although by far, the wanton rape, murder, and execution of innocent civilians fell greater upon the former. In January 1919, at the initiative of Representative José T. Canales of Brownsville, the Texas Legislature launched a full investigation of Rangers' actions throughout these years. The investigation found that from 300 up to 5,000 people, mostly of Hispanic descent, had been killed by Rangers from 1910 to 1919 and that members of the Rangers had been involved in many sordid misdeeds of brutality and injustice.