CIUDAD JUAREZ, Mexico -- Half of the drivers who work a bus route on which two colleagues were shot to death last week, possibly by a woman seeking revenge for purported sexual abuse of female passengers, didn't show up for their jobs Tuesday.
Only 10 of the 20 drivers assigned to the 4A bus route in this border city took the wheel, "because they are afraid," a dispatcher said.
"There were a lot fewer passengers, too," said the dispatcher, who refused to be quoted by name out of fear of being targeted. "Everyone is afraid something could happen," he added.
Officials said plainclothes police officers were aboard some buses and conducting weapons searches to prevent further killings.
Mexican prosecutors released a police sketch of a female suspect drawn from the testimony of at least 20 witnesses. It shows a woman wearing a sun visor over hair pulled back on her head.
They said they were looking into claims made over the weekend in an email from the self-styled "bus driver hunter," who said she is seeking revenge on behalf of fellow women who she alleged had been abused by bus drivers in Ciudad Juarez, which is across the Rio Grande from El Paso, Texas.
The claims echoed deeply in Ciudad Juarez, which has a grim history of sexual violence against women aboard buses.
Authorities say a woman wearing a blond wig, or dyed hair, boarded one of the school bus-style vehicles that serve as transport in Ciudad Juarez last Wednesday morning. She approached the driver, took out a pistol, shot him in the head and got off. The next day, apparently the same woman did exactly the same thing to another driver on the same route.
Over the weekend, media outlets began receiving emails from the address "Diana the hunter of bus drivers."
"I myself and other women have suffered in silence but we can't stay quiet anymore," the email said. "We were victims of sexual violence by the drivers on the night shift on the routes to the maquilas," a reference to the border assembly plants that employ many residents in Ciudad Juarez, across the border from El Paso, Texas. "I am the instrument of vengeance for several women."
The newspaper Diario de Juarez reported that a witness quoted the killer as telling the second victim, "You guys think you're real bad, don't you?" before shooting him.
Authorities have not verified the authenticity of the email, or of a Facebook page set up under a similar name Aug. 31.
But Arturo Sandoval, spokesman for the Chihuahua state prosecutors' office, said the vigilante claim was considered one of the working hypotheses in the crimes. There was no apparent robbery.
"Now that we have the email in the case file, it indicates that this could have been someone who had a run-in with a driver or one of his relatives," Sandoval said.
Many of the women murdered during a string of more than 100 eerily similar women's killings in Ciudad Juarez in the 1990s and early 2000s disappeared after boarding buses. Their bodies were often found weeks or months later, raped, strangled and dumped in the desert or vacant lots.
Several bus drivers were arrested in connection with those killings, but the cases against them always appeared weak, or their confessions coerced. One driver had his conviction overturned, and his co-defendant, another bus driver, died in prison before sentencing.
Associated Press writer Mark Stevenson in Mexico City contributed to this report