The man decapitated in an apparent Islamist attack on a chemical factory in France was the assailant's boss, according to French reports, as police questioned the prime suspect's wife and sister.
The victim, aged around 45, ran a delivery company authorised to enter the Air Products liquid gas factory in Saint-Quentin-Fallavier, outside Lyon, where the attack took place yesterday morning.
The unnamed man's head was found attached to a fence outside the factory, far from the body inside the site.
Beside it was a black flag with inscriptions in Arabic, thought to be those of the Islamic State of Iraq and the Levant.
Yassin Salhi (35) the man arrested inside the factory after smashing into liquid gas canisters causing an explosion and fire, managed to enter the sensitive site in a vehicle belonging to the company and which had security clearance to do so. According to security camera footage seen by AFP, he had first planted the head outside before entering the plant.
"This was a terrorist attack given that a corpse was found decapitated and with inscriptions," said president Francois Hollande, who returned early from a European summit in Brussels to chair an emergency security meeting on Friday afternoon.
After ramming some gas tanks at "high speed", Salhi then got out of his vehicle and ran into a nearby building to try to open the valves of more liquid gas bottles, in a bid to spark a far bigger explosion.
However, one of two firemen called to the scene tackled the suspect to the floor as he shouted "Alahou Akbar" (God is Greatest).
Bernard Cazeneuve, the interior minister, called the firefighter's act one of extreme "bravery and sang-froid". Salhi suffered superficial facial injuries in the struggle.
Salhi (35), of North African origin from Saint Priest in eastern Lyon, has "no criminal record", according to Mr Cazeneuve.
He was listed in 2006 as a Salafist "radical", but went off the radar in 2008. According to RTL, intelligence agents voiced alarm about his "radicalism" as recently as last year.
Police said that a person "close to" the arrested suspect was detained suspected of conducting "reconnaissance" at the site before the attack, but later released.
The suspect's sister and wife were also taken in for questioning. Beforehand, the wife expressed total ignorance and shock on Europe 1 radio, saying her husband was at work, apparently doing deliveries.
"My heart is going to stop. I don't know what has happened. Have they arrested him?" she asked.
"He went to work this morning at 7am. He does deliveries. He did not return between noon and two, I expect him this afternoon.
"My sister said turn on the television. She was crying," said the young woman. "I know my husband. We have a normal family life. He goes to work, he comes back," she said.
"We are normal Muslims. We do Ramadan. We have three children and a normal family life," said the wife of the suspect.
Shocked neighbours said the Salhi, his wife and three children aged six to nine were "very discreet". They had arrived in the district around six months ago.
There remain question marks over whether the assailant had acted alone.
Mr Hollande said: "The attack carried out by one person, perhaps accompanied by someone else rammed at high speed this establishment, and contains gas tanks. This was a terrorist attack."
Saying he expressed "solidarity" with the victim, he added it was all the more painful given the Islamist attacks of January in Paris in which 17 were killed, which rocked the nation.
"But emotion cannot be the only response: we need action, prevention dissuasion and the necessity to carry our values and never give in to fear."
Manuel Valls, the prime minister, who is on a tour of South America, called on sensitive sites in the Rhone-Alpes region to remain "highly vigilant" in case of follow-up attacks.
"France has been struck again by terror," says Mr Valls, who is cutting short the trip to return to Paris.
Patrick Menucci, Socialist MP of the Bouches-du-Rhône area, said: "France is at war."
"I know it's not good to say so, but this terror attack in Saint-Quentin-Fallavier is the proof," he told Le Monde.
"We have on our territory individuals who don't obey the laws of the Republic but fatwas of the Islamic State," said Mr Menucci, two months after the Senate issued figures suggesting that half of all Europeans having left the continent to wage jihad in the Middle East were French.
In all 1,683 French nationals are in some way implicated in the fighting - a 203pc increase in
Mr Menucci said in this case it appeared the attacker was not a returning jihadi but part of a "sleeper cell", like Mohammed Merah, the Toulouse killer.