The black sedan glided up to the Las Vegas hotel where Elizabeth Suarez was waiting to take an Uber home after a night of gambling. She recalled asking the driver: Are you waiting for Liz? Yeah, he responded. Get in.

She had done it countless times. But that night in July 2018, as the man veered off course toward a deserted parking lot, as he cranked up the radio and ignored her questions, as her real driver called her wondering where she was, Ms. Suarez said she realized with horror: This was not an Uber.

“That’s when he said, ‘Give me your wallet, give me your phone, give me everything you have,’” Ms. Suarez, 28, said.

On busy streets outside bars or clubs, people often hop into a car without a second thought. But the killing of Samantha Josephson, a 21-year-old college student in South Carolina who was stabbed to death after getting into a car she mistook for her Uber last weekend, has brought national attention to a rash of kidnappings, sexual assaults and robberies carried out largely against young women by assailants posing as ride-share drivers.