One of his schoolmates, who requested not to be identified, said Tilao came from a broken family. His parents separated when he was very young.
Tilao attended primary school in Malawi and high school in Isabela City in Basilan. He apparently wanted to become a policeman because he moved to Zamboanga City where he took up criminology at the Zamboanga Arturo Eusta-quio Colleges from 1982 to 1985. The school, however, expelled him for misdemeanors.
He also took up the Naval Reserve Officers Training Course at the Zamboanga School of Arts and Trade from 1982 to 1984, also in Zamboanga City.
"Aldam was a nice guy. But he was naughty," a schoolmate said.
Jailed Muslim leader Nur Misuari revealed earlier that Tilao had tried to join a mujahedin training camp in the Middle East, but was similarly expelled for bad behavior.
That failure provided an opportunity for Tilao to train with Abu Sayyaf founding chief Abdurajak Abubakar Janjalani, who was slain by police in a clash in December 1998 in Basilan.
Tilao proclaimed himself successor to Janjalani sometime in 1999.
Tilao had returned from Saudi Arabia where he was an overseas Filipino worker. During his stint in Saudi Arabia, the Abu Sayyaf engaged in high-profile atrocities and extortion.
Janjalani’s younger brother, Khadaffy, was expected to succeed Janjalani to the post of Abu Sayyaf chief. However, Khadaffy despite the blood ties lacked ideological grounding and training in terrorism.
Military files obtained by The STAR revealed that Tilao was born in Barangay Carbon in Malamawi, an island less than a kilometer north of Basilan, on July 18, 1962 to Arola and Marcusa Tilao.
Under the section "distinguishing characteristics" on file, he was described as "hot-tempered."
Tilao had two wives. The first was Rosanna Halong, a nurse currently working in Saudi Arabia. They have a son, Ahmad.
His second wife was Hamja Salma Halid, from Barangay Tinga in Talipao, Sulu. They were married Aug. 19, 2000. He was divorced from her in July last year.
Tilao had three brothers. One was killed in a crossfire in 1999.
He has a sister who is married to a retired Army major and a half-brother and a half-sister.
It was not clear when he joined the Moro National Liberation Front (MNLF) before joining Janjalani to form the Abu Sayyaf in the late 1980s.
The military files revealed that Tilao had undergone training in Libya. Janjalani had also trained in the Middle East and joined the Afghan mujahedin in fighting the then Soviet occupation forces in Afghanistan before founding the Abu Sayyaf.
Tilao gained prominence in the mass abduction in March 2000 of some 20 pupils and teachers, including Catholic priest Rhoel Gallardo, in two schools in Sumisip and Tuburan, Basilan.
During the crisis, Tilao introduced himself for the first time as Abu Sabaya to the media. He also took the aliases Abu Ahmad Salayuddin and Sumaya.
In the March 2000 hostage crisis, Gallardo was tortured and killed. Two male teachers were beheaded while a female teacher was also killed.
Journalists who knew Tilao well described him as media savvy and publicity hungry. In such a short time, Tilao propelled himself to prominence, even calling up radio stations and foreign news agencies.
It is also said that Tilao wanted to become the Abu Sayyaf leader because he had foreign training unlike Khadaffy Janjalani.
Last year, Tilao embarrassed President Arroyo by beheading American hostage Guillermo Sobero, saying his head was their "Independence Day gift" to her. Four months later, Sobero’s remains were found.