Last week, a Mexican college student disappeared after she got in a car from Cabify, a ride-sharing app similar to Uber, in the city of Puebla. On Friday, Sept. 15, she was found dead in a neighboring state.

Authorities say Mara Castilla, 19, was murdered by her Cabify driver in a motel and disposed in a bed sheet (link in Spanish). The alleged killer was identified only as Ricardo N.

Promises to harshly punish the driver were little comfort to the family of Castilla, who was studying political science and still enjoyed Disney movies, according to her mother —or to the thousands of ride-sharing app users in Mexico. The tragedy has been a chilling reminder to them that the neat, algorithm-dominated world of mobile apps is not immune to the country’s unbridled crime.

Wary Mexicans have long avoided taking random taxis off the street, and tourists are told to only rely on cars provided by their hotels. But people quickly took to Uber and Cabify. The driver information and location technology in the apps gave them a sense of security, and the two companies have rapidly expanded in Mexico in the past few years.

The Castillo case will give many of their users pause. Debates over whether Cabify shares responsibility in the murder have flared up on social media. Some accuse the company of not properly screening its drivers. Others say the problem is much bigger, and starts with Mexico’s failing justice system. Still others put blame on Castilla, who hailed the Cabify car at 5am after spending the night at a bar with friends, according to media reports.

Some are saying they’ll never use ride-sharing-apps ever again.

Before Castilla’s death was known, Cabify said its security protocols are the strictest in the market, and that its technology was helping provide useful information to investigators looking for her. Activity on Castilla’s cell phone, too, was a big clue toward uncovering what happened.

The company declined to provide details about its screening methods to Quartz on Saturday, out of respect for the family’s mourning, it said. State officials have said they are looking into taking measures against Cabify (link in Spanish).