At age 16, as Daood Gilani, he was taken out of Pakistan, where he attended a military school, and brought to Philadelphia by his mother, a well-known Old City nightspot owner.
Today, under the name of David Coleman Headley, he sits in a federal prison in Chicago, charged by the FBI with planning terrorist attacks overseas - including an alleged plot to target the Danish newspaper that in 2005 angered Muslims with a cartoon of the prophet Muhammad.
Federal agents arrested Headley, 49, last month at O'Hare International Airport in Chicago as he prepared to board a plane to Philadelphia, where he still has relatives. Philadelphia was a stopover on a trip to Pakistan, according to the criminal affidavit.
In his luggage, he had a copy of the Danish newspaper's front page and a memory stick that included videos of the paper's front entrance.
"Everything is not a joke," he wrote in an e-mail to fellow classmates at his old military school, according to the federal complaint. ". . . Call me old-fashioned but I feel disposed towards violence for the offending parties."
After his arrest, he admitted to the FBI that he was surveilling the paper and Danish troops stationed nearby in preparation for an attack, the criminal affidavit states.
Headley was being held without bail on charges of conspiracy and providing material support to terrorists, pending a hearing.
Unlike some other federal terrorism cases, where the alleged plotters were really only talking to undercover agents, the case against Headley alleges that he was in contact with known leaders of terrorist groups in Pakistan.
According to the charging documents, federal authorities tracked his meetings, e-mail, and phone conversations.
He admitted to the FBI that he trained with Lashkar-e-Taiba, a terrorist group, and that he was working with Ilyas Kashmiri, operations leader of another Pakistani terrorist organization.
Indian authorities also suspect Headley, a U.S. citizen, may have scouted targets in Mumbai before the attacks last year that killed 165 people, according to a report in the Washington Post.
There is no evidence of a threat to Philadelphia, two law enforcement sources said last night.
Federal authorities in Chicago also said there was no apparent link to any domestic terrorist conspiracies.
The pending federal case is centered on an alleged plot against the Danish newspaper Jyllands-Posten, which angered Muslims around the world by publishing a cartoon in 2005 of the prophet Muhammad with a bomb in his turban.
In phone calls, Headley and the other conspirators called it the "Mickey Mouse project" or the "northern project."
After his arrest, according to the federal documents, Headley told the FBI that he proposed scaling down the operation, from attacking the building to killing the paper's cartoonist and cultural editor.
Headley's attorney, John T. Theis of Chicago, declined to comment yesterday.
Headley, born Daood Gilani, is the son of a prominent Pakistani diplomat and the late Serrill Headley, founder and former owner of the Khyber Pass pub/restaurant at 56 S. Second St.
Serrill Headley, who grew up in Bryn Mawr, split with her husband, and lost custody of her children in Pakistani courts. "In Pakistan, men own the children. There are no rights for women," she said in an interview in 1974.
After 10 years in Pakistan, Serrill Headley moved to Philadelphia, bought a 100-year-old tavern in 1973, and turned it into a bustling nightspot.
After two earlier attempts to get her son out of Pakistan failed, she succeeded in 1977.
In Philadelphia, however, he suffered from culture shock. Raised as a Muslim, he was having trouble adjusting to the idea that his mother ran a bar, an Inquirer column said.
"He has never been alone with, much less had a date with, a girl, except the servant girls of his household," an Inquirer column said back then.
At the time, the Khyber was a slice of exotica on the Philadelphia bar scene, with Pakistani wedding tents and 180 brands of beer.
Eventually, Serrill Headley turned it over to her son.
"His mother owned it and gave it to him around 1985," said Stephen Simons, current owner of the bar, now called the Khyber.
"He ran it for about a year and ran it into the ground," Simons said. Simons' brother bought the bar in 1988.
David Headley studied accounting, possibly at a community college in the Philadelphia region. With his mother, he operated a video store, FliksVideo, in Center City.
Serrill Headley died in 2008. Her second husband, Dick Pothier, was an Inquirer reporter; he died in 1995.
In 1997, Headley, under his birth name of Gilani, was convicted on federal charges in Brooklyn of smuggling heroin into the country. He was sentenced to 15 months in prison.
Family members in published reports have described his striking eyes - one blue and one brownish-green.
He changed his name to Headley in 2006. In August, in an interview with Customs agents, he said he changed his name to raise less suspicion when he traveled.
Headley had been living in the north side of Chicago, authorities said, in an apartment under the name of a dead man. Although he has claimed to be a consultant in an immigrations business, federal agents who have had him under surveillance found no evidence that was true.
Still, they said he has traveled extensively since 2006, including trips to Pakistan, India, and Denmark. Sometimes he traveled to Pakistan for months at a time, they said.
The FBI was listening in as Headley and another man arrested in the case, Tahawwur Rana, 48, also of Chicago, discussed attacking the National Defence College in India, the charges say.
Both Headley and Rana, a self-described immigration consultant who attended the same military school in Pakistan, were in regular contact with known terrorists in Pakistan, including groups with links to al-Qaeda, they say.
Headley allegedly planned the attack in Denmark along with Kashmiri, the operations chief of a militia fighting NATO forces. Reports have linked him to al-Qaeda and say he established a training camp in Waziristan, Pakistan.
In September, news reports said Kashmiri was killed in a drone attack. Headley was recorded talking in coded language about Kashmiri's death, saying the "doctor" may have "gotten married" - code for killed - and how that might affect "investments," code for violent attacks, according to the federal charges.
"It has made me very sad," Headley said, as FBI agents listened.
But the reports were wrong. Kashmiri was not killed. Headley rejoiced.
"Buddy, if this is true, then I will say 100 prayers, 100 prayers," Headley said.