His slayings are particularly savage, and his trademark is to pound in his victim's skull with a sledgehammer or heavy rock, cover the head with a blanket, then toy with the body as it dies.
Surveying a recent murder blamed on the Railroad Killer, Police Chief Randy Kennedy from Hughes Springs, Texas shook his head. "He's really, really vicious," said the veteran cop. What's more, the killer does not hurry away into the night, but lingers to raid the refrigerator and rifle through drawers in his victims' homes.
The American authorities suspect that a short Latino man with spectacles has committed at least eight murders - six of them within the past nine weeks. When it came to light that, on 1 June, immigration officers deported a Mexican man fitting the Railroad Killer's description, right down to the tattooed serpent and scars on his left forearm, but simply shooed him to the middle of a bridge over the Rio Grande and waved goodbye, there was fury and disbelief on both sides of the border. But mostly there was fear. An unpredictable serial killer is on the loose, and the trains are running in all directions.
Texas marshals, policemen and agents from the FBI have launched an intensive manhunt which has resulted in more than 2,000 leads from the public. The government put a wanted poster for the fugitive - Rafael Resendez-Ramirez - on the Internet, and listed 30 different aliases for him. From Wyoming to Kentucky, reports came in that Resendez-Ramirez, the infamous Railroad Killer, had been spotted on the run. Hispanics complained about a hate backlash as a result of the publicity. Police halted a freight train in Columbus, Ohio, and searched all 75 cars with sniffer dogs after a panicked housewife glimpsed a Latino man on board.
Meanwhile, in northern Mexico, a switchback road climbs towards Rodeo like a sidewinder through the high scrub mountains north of Durango. It's a dusty small town, over 300 miles from the Texas border, and a notorious black-market centre for cannabis and hot cars. These provide far bigger profits than the local chillies and pinon nuts. Strangers are given a wide berth here and their questions are dodged. Family vendettas are rife and retribution is quick. When the Medina and Renteria families feuded in the early 1990s, 30 people were slain in quick succession: no one else wants to end up shot dead while drinking coffee in the town's cafe - whatever the reason.
Harbouring a mild-mannered serial killer would be easy in Rodeo. Two days after his Most Wanted poster was tacked up in the drugstore, following the visit of two FBI agents to the health clinic where the murder suspect's common-law wife works, it had already been torn down.
A local policeman, Rodolfo Ramirez Ceniceros, recounts how Angel Resendiz, the eccentric part-time English teacher at the town's convent school, was quietly reading the newspaper and eating a taco several weeks ago when he stopped in the middle of both actions. Abruptly, he folded the paper, paid his tab, and just took off. Inside that paper was the first Mexican article about the Railroad Killer. News of the murders had finally reached the suspect's home town, weeks after the frenzy in the States began. But putting the "genuine" name, Rafael Resendez-Ramirez, in bold type above all the other aliases gave extra time for the alleged murderer to slip away. Not until the mugshot photos came out on satellite television did anyone in Rodeo catch on to the fact that the suspected slayer was Angel Resendiz.
Julieta Dominguez Reyes, a lab analyst at Rodeo's public health clinic, hasn't missed a day of work in eight years. But last Saturday she stayed home as she came to terms with the information that her lover and the father of her baby is probably the Railroad Killer. She has dropped nearly a stone in weight and slept very little since Angel Resendiz left home in a hurry on 10 June, after a phone call warning him that police were searching for him in Puebla, his birthplace.
"We've been living together five years and I had no idea about this. He never was violent or sadistic. He was a gentleman in all the small details. He never failed to open the car door for me," she insisted. "But if he did what they are saying, his spirit is rotting and his mind must be disturbed," Julieta said in a quiet voice, holding their baby Liria on her lap. "My Angel refused to turn himself in, or to repent and ask God's blessing. He told me: `It's better to run. I cannot stand prison. They're pursuing me and there's no alternative.' "
Shortly afterwards, two law officers, one American, the other Mexican, came to her tidy white house to haul away a bundle of Angel's clothing, his bike and his guitar for forensic tests. They also gathered pay-cheque stubs, as well as more than 100 pieces of jewellery which they will try to link to victims. When she surrendered these, the enormity of her lover's crimes sunk in, and Julieta felt overwhelmed. "You don't know what is inside a man's head. But we were a very stable couple," she stressed.
They used to live for a month or two together in Rodeo, then Angel would go north illegally, as he had since the age of 16, as a migrant worker in the tobacco fields of Kentucky, or the asparagus fields of Washington. He'd pick oranges in California or harvest rice in Texas. Sometimes he got odd jobs in gas stations, but it was usually in agriculture. According to Julieta, he has a green thumb. Angel sent home $140 (pounds 90) a month, far more than the $6 a week the local nuns paid him for teaching English without a credential. He'd picked up the language on the road, and held forth in conversational English classes at Fray Bartolme de Casas, a convent school opposite the police station.
Border-crossing was not without its benefits either: Resendiz could get $400 a head for shepherding illegal aliens into Texas, and on the way back he'd drive recent model cars and sell them for a profit in Mexico.
Although Angel never seemed keen about trains particularly, Julieta knew he rode them on occasion. "But I never suspected him of keeping secrets," she said. "He told me about one conviction in 1988. Also about some group he joined in the States that was anti-homosexual and anti-abortion."
Julieta is too overwrought to ponder how much their child will take after her father, but wants to keep her husband's dark legacy from affecting their baby. "He loved his daughter almost too much. He kept saying how she was so beautiful." Black-eyed Liria has a shock of black hair and, in some moods, resembles her father's mugshot. "Innocence is redemption," Julieta said, tears welling in her weary eyes. "The baby is the most important thing."
Four-year-old Lupe Abitia Valdez lives across the street from Angel Resendiz's white-painted bungalow. She is shy, but likes to play in the teacher's garden. Together with her eight-year-old sister Alexis, Lupe recently went to her neighbour's house to munch corn chips in the living- room and watch the video that the suspected Railroad Killer Resendez shot at her birthday party on 8 June.
"We have had no problems with our neighbour," said Lupe's father, Salsido Abitia, a primary school principal. "He was so happy when we invited him to the birthday party. He videoed it and he kept the cassette. After reading the newspapers, I was terrified. In all the 55 years that I have lived in Rodeo, I never felt this way." Abitia puts a protective arm around both his daughters.
In spite of the years he has spent living in this small community - even running unsuccessfully for local office back in 1993 - Angel Resendiz is still considered an outsider in Rodeo. He joined his mother and half a dozen half-siblings a few years after they moved from Puebla in 1991. He has two brothers: one a gospel preacher in Chihuahua and the other a customs official at Juarez. A close friend of the family said that his mother, Virginia Resendiz de Maturino, used to pray for a distant son who "wandered about lost", but otherwise never mentioned him. One day, Angel just turned up unannounced.
Law enforcers on both sides of the border want to be ready the next time he appears.