PARIS - Yassin Salhi was a quiet man with a job, a family and no criminal record before he allegedly launched a grisly assault at an industrial gas factory in France and pinned his boss's severed head to the fence on Friday.
While authorities had investigated the married 35-year-old father of three for ties to the radical Salafist movement, he was never identified as participating in terrorist activities and never convicted of a crime.
A co-worker of Salhi's said he was mysterious, possessed of a quiet strength and deceptively calm.
"He was a wolf in sheep's clothing," Abdel Karim told RTL radio.
"He had already talked to me about Daesh," said Karim using one of the names for the Islamic State group.
It was "not to indoctrinate me into anything, but simply to ask me my opinion. When I told him what I thought, from that day on, it was 'Hello/goodbye.'" Salhi caught the attention of intelligence authorities in 2005 and 2006 because he was socialising with a group of people associated with radical Islam, a source close to the case told AFP.
Intelligence services investigated him for a few years thereafter, but did not renew their inquiry in 2008, French Interior Minister Bernard Cazeneuve said.
"This individual has links with the Salafist movement, but had not been identified as having participated in activities of a terrorist nature," he added.
'He was nice'
He was born in the eastern French town of Pontarlier, near the border with Switzerland, to a father of Algerian origin and a mother with a Moroccan background.
The death of his father while still a teen and the subsequent upheaval in his life provides a potential clue of what may have opened the door to radicalisation in his youth.
But after his father died, his mother sold the family home and moved the family away.
"He was alone, he was probably the ideal target for the radicals looking for prey," said Nacer Benyahia, the imam of the mosque Salhi attended as a boy.
Salhi "was a calm kid, he wasn't highly strung. It was a pleasure to have him at the mosque. He was nice," said Benyahia, who heads the mosque in Pontarlier.
Authorities know Salhi lived for a time with his wife and three young children in the eastern city of Besancon.
He popped up again on the intelligence services' radar in 2013 because he was associating with people suspected of links to radical Islam. At the time he wore a beard and a traditional North African robe called a djellaba.
But apart from his appearance there was nothing concrete to indicate he was up to anything dangerous, the source said.
Finally at the end of 2014 Salhi moved his family into a low-income apartment building in Saint-Priest, a quiet suburb of France's second city, Lyon.
Earlier this year he began working as a delivery driver. His boss, or one of his superiors, was the target of Salhi's alleged violence, which erupted Friday with his assault on the gas factory.
The man's severed head was found pinned to the gate at the facility with Islamist flags draped near it.
A woman identified as his wife said in a French radio interview she was shocked by his alleged actions.
"On the news they are saying that it's a terrorist attack, but that's impossible. I know him, he's my husband. We have a normal family life," the unnamed woman told Europe 1 radio.
"My heart is going to stop", said the woman, whom the radio station identified as Salhi's wife. "He went to work this morning at 7:00am." "We are normal Muslims, we're observing Ramadan. Normal. We have three kids, a normal family life," she said.