Appealing to the Rangers for help, ranchers near the tiny border town of Porvenir persuaded Captain Fox that residents of the town were responsible for recent raids on their property. In January of 1918, Captain Fox dispatched eight Rangers to investigate the matter, while he stayed behind. The Rangers conducted their interrogations late at night, rousing residents from their beds for questioning. But the interrogations were inconclusive, and those who had been detained for questioning were released. Not satisfied, the Rangers planned another late night visit to search for weapons.

On the night of January 28, 1918, as the U.S. Army set a perimeter around the town, the Rangers and local ranchers turned the Porvenir residents out of their homes, and separated fifteen men from the rest. The next morning, the entire group of fifteen Mexican civilians were found dead at Porvenir. According to Ranger accounts, they came under fire while conducting their search, and began shooting back. According to local residents, the fifteen men were executed en masse. The victims included Antonio Castañeda, Longino Flores, Pedro Herrera, Vivian Herrera, Severiano Herrera, Manuel Moralez, Eutimio Gonzalez, Ambrosio Hernandez, Alberto Garcia, Tiburcio Jáques, Roman Nieves, Serapio Jimenez, Pedro Jimenez, Juan Jimenez, and Macedonio Huertas. Captain Fox did not document these events in his monthly report.

But a Porvenir resident named Harry Warren had recorded the names of the murdered men and their families and was demanding justice. Following state and federal investigations, Governor Hobby disbanded Company “B” and fired five of Fox’s Rangers. Adjutant General Harley attempted to transfer Fox to a desk job in Austin, which Fox refused. Instead, he tendered his resignation, believing that his men had only been performing their duties. Harley felt differently, that the problem “centered on the issue that fifteen men had met their deaths in Ranger custody, ‘after being arrested and disarmed’.” (Ritter 57)