Uber driver Keith Avila picked up a passenger who looked like a 12-year-old girl in a short skirt Monday night. That was the first sign that something was off, he would say later.
Two women got into his car with the girl outside a house in Sacramento. Halfway to their destination - a Holiday Inn in Elk Grove, Calif. - they asked Avila to turn up the music, he said.
Then the women turned to the girl. Avila listened in.
"They were describing what they were going to do when they get there: 'Check for guns. Get the money before you start touching up on the guy,'" Avila said on Facebook Live minutes after he dropped off the passengers, then called police to report the women whom he suspected of prostituting the child.
The girl was 16, not 12, Elk Grove police told local news outlets. But Avila's suspicions were right, they said. The teen was being sold for sex at the Holiday Inn, and her eavesdropping Uber driver had saved her.
A 34-year-old husband, father and quinceañera photographer by day, Avila had started driving for Uber just a few weeks earlier, the Daily Beast reported. Monday's fare made him an instant celebrity.
"The police is just right there; look at that!" Avila said in the Facebook video, as blue lights flashed in his rear windshield.
Outside, in the hotel parking lot, police were arresting Destiny Pettway, 25, and Maria Westley, 31, on charges of pimping and threatening a minor.
"I told police, 'If you don't come, I'm going to go in there myself and take pictures of these guys,'" Avila said on Facebook. "That's not a good life, to be under the control of another human being for the purpose of sex trafficking."
He said he even gave police the hotel room number after overhearing the girl call her john, "probably some douche-bag pervert," he said.
Police said they caught Disney Vang, 20, in the hotel and "determined that [he] had been involved in unlawful sexual activity with the victim." Vang was arrested and charged.
"He could have said nothing and gone on his way and collected his fare," Elk Grove police spokesman Christopher Trim told Fox affiliate KTXL. "And that 16-year-old victim would have been victimized by who knows how many different people."
The girl - apparently a runaway - was taken "to an alternative housing location," according to the authorities.
"She was reunited with her family," Avila told the Daily Beast. "I felt kind of good about that."
In 2010, the National Center for Missing and Exploited Children's president told Congress that at least 100,000 American children, mostly runaways, were prostituted each year - although The Washington Post's Fact Checker found scant evidence to support that figure. A study this year based on interviews with hundreds of people involved in the trade put the figure closer to 10,000.
Whatever the exact number of victims, prostitution has long concerned American leaders.
In a 2012 speech, President Obama said such human trafficking "ought to concern every person, because it is a debasement of our common humanity."
"When a little girl is sold by her impoverished family - girls my daughters' age - runs away from home, or is lured by the false promises of a better life, and then imprisoned in a brothel and tortured if she resists, that's slavery," Obama said. "It is barbaric, and it is evil, and it has no place in a civilized world."
And yet, the president noted, it "also goes on right here. . . . The teenage girl, beaten, forced to walk the streets. This should not be happening in the United States of America."
Last year, at a news conference to discuss a federal anti-trafficking initiative, Attorney General Loretta E. Lynch noted that "human traffickers prey on some of the most vulnerable members of our society to exploit them for labour, for sex and for servitude of all kinds. Their crimes, appropriately described as modern-day slavery, have no place in a nation that has overcome the scourge of slavery."