GUADALUPE DISTRITO BRAVOS, Mexico — Her uncle, the mayor who gave her the job nobody else wanted, warned her to keep a low profile, to not make too much of being the last remaining police officer in a town where the rest of the force had quit or been killed.

But in pictures for local newspapers, Érika Gándara, 28, seemed to relish the role, posing with a semiautomatic rifle and talking openly about the importance of her new job.

“I am the only police in this town, the authority,” she told reporters.

Then, two days before Christmas, a group of armed men took her from her home, residents say, and she has not been seen since.

It was an ominous punctuation mark on the wave of terror that has turned this cotton farming town near Texas into a frightened outpost of the drug war. Nearly half of its 9,000 residents have fled, local officials say, leaving block after block of scorched homes and businesses and, now, not one regular police officer.