Adel Kermiche, 19, had been known to the French authorities before yesterday's shock church attack in a Normandy town and was described by one acquaintance as a "time bomb".
Kermiche and another unidentified man stormed the centuries-old stone church in Saint-Etienne-du-Rouvray, taking priest Jacques Hamel hostage along with three nuns and two worshippers before slitting the elderly cleric's throat.
He lived in his parents' modest home -- less than two kilometres from the church -- where he spent much of the day under curfew, fitted with an electronic tag while awaiting trial for alleged links to terror.
German authorities arrested him shortly afterwards as he attempted to transit the country using his brother's identity.
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He was returned to France where he was detained on March 23 last year for "criminal association in connection with terrorism" and preparing a terrorist act. He was released on bail but banned from leaving the Seine-Maritime region of northern France.
Six weeks later he fled the family home once again and was ultimately traced to Turkey where he was detained on May 13 last year.
"We knew he wanted to go to Syria," said a 60-year-old neighbour of the assailant's family, who added that he "never saw him go to the mosque" that the family attended.
"He never spoke to us," said the neighbour.
"The last time I saw him was on Friday. He was playing football in his garden."
Sister Danielle, a nun who managed to escape the hostage situation and alert police, described how the attackers made Hamel kneel at the altar in his white vestments.
"They recorded it. They did something like a sermon around the altar in Arabic," she added.
Danielle then fled the church in a daring escape after which she was able to call police.
Three other hostages escaped unharmed while one worshipper had severe knife injuries to his throat.
One of Kermiche's acquaintances, a youngster from the area of Saint-Etienne-du-Rouvray, told Le Parisien newspaper that he was a "hyperactive child" who was excluded from school at the age of 12 due to "behaviour issues" -- adding that he was a "time bomb".
French daily Le Monde reported that Kermiche had struggled with psychological issues for much of his life, having been monitored from the age of six and hospitalised on several occasions in his teenage years -- including 15 days in a specialist psychiatric unit.
Another of the town's residents, a teenager who said he knew the attacker, told RTL radio he was not surprised by what happened yesterday.