In Saudi Arabia, Vahey displayed an openness and concern for children that people would remark upon for the rest of his career, said Max Crum, a 38-year-old former student.
"When you're a kid, and you have teachers who are stern and mean, you kind of fear them. He wasn't that at all," Crum said.
By 1992, Vahey and his wife moved to the prestigious Jakarta International School in Indonesia, where he again taught social studies, coached basketball and developed a reputation for leading fun overnight trips for students.
"All the kids seemed to really, really like him," said Will Julius, a 21-year-old alumnus and son of a former longtime International School teacher.
After 10 years the Vaheys moved to Escuela Campo Alegre in Venezuela, where Jean became superintendent and the man known to all as Bill took a teaching job at the sprawling hillside campus overlooking the capital, Caracas.
All new hires were required to provide a police record from either their home of record or their last country of assignment, if they had been there for more than five years. Vahey presented one from Indonesia with no history of problems.
Again in Venezuela, the popular teacher and family man took students on trips
Authorities may have missed a warning sign when two students under Vahey's care were rushed to a hospital after falling unconscious in their hotel room during a trip to a basketball game, parents and staff said. A toxicity test came back negative, so the school sent security officials to investigate. They were unable to determine a cause and chalked the incident up to a possible failing air conditioning unit. Vahey was not investigated.
Vahey also privately organized outings like a weeklong annual trip to Costa Rica for some 20 to 25 students, parents and staff said.
Superintendent Gregory Hedger said that when he arrived he was surprised to learn such excursions were allowed. He put an immediate stop to trips not sponsored by the school and without parent chaperones.
Seven years later, the Vaheys went to work at the Westminster campus of London's Southbank International School, which has about 350 pupils from 70 countries. Vahey was subjected to two criminal background checks in the United Kingdom, where he hadn't lived before.
After a year, Vahey founded the "Travel Club," according to a 2012 article in Focus, a magazine for expatriates in London. The school's website describes a 13-day trip to Nepal in 2012 that included a trek in the Himalayas, white-water rafting and an elephant safari. In 2013, the spring break trip by students in grades six to nine was to Panama.
Southbank's chair of governors, Chris Woodhead, told Britain's Press Association there had been one complaint against Vahey. A boy on a trip felt sick, Woodhead said, and Vahey took the child into his room, apparently "to look after him."
"A few months later a teacher heard gossiping on a minibus and the incident was investigated," Woodhead said. "The boy's parents agreed that there was nothing untoward and the matter shouldn't be pursued."
When Vahey went on to the American Nicaraguan School with glowing references, his wife stayed in London.
In Nicaragua, Vahey taught ninth-grade world history and advanced geography in such an exciting way that students asked why other teachers couldn't do the same. He drew little notice from his neighbors until days before Thanksgiving.
That weekend, after Vahey's maid was fired for stealing, he stopped leaving the house, said Rafael, a caretaker who declined to give his last name because of the sensitivity of the topic. All Sunday, the house was dark. On Monday, school employees who let themselves in with a master key found Vahey motionless in his bed.
Two groups of emergency officials declared him dead and called the coroner. The school's director, Gloria Doll, sent teachers and parents a message saying Vahey "will be greatly missed, as he has truly been an integral part of our community."