Yassine Salhi, suspected of carrying out an attack at a French industrial gas factory on Friday, was also allegedly involved in an anti-Semitic attack in 2012.
Salhi, 35, a married father of three, is known to have ties to Salafist radicals in France, and was under surveillance from 2006 to 2008.
Three years ago, Salhi and another man allegedly hit a Jewish teenager and Salhi allegedly hurled anti-Semitic abuse at him while they were traveling on a train from Toulouse to Lyon.
A French prosecutor said Friday there was no sign that Salhi, alleged to have carried out the beheading of his boss and tried to blow up the factory, had an accomplice.
Salhi entered the factory with ease at the wheel of a delivery van which he often drove to the site, where “he was known to employees,” prosecutor Francois Molins told reporters.
On Friday morning, Salhi drove into the Air Products gas and chemicals factory at 9:28 a.m. (7:28 GMT) local time, and disappeared from the vision of security cameras until 9:35 a.m. when the van was seen accelerating towards one of two hangars by one of two cameras.
A minute later a massive blast was heard.
Firefighters were called and arrived at the site at 9:41 a.m. At 10:00 a.m. they found the suspect inside one of the hangars which contained bottles of gas, liquid oxygen and highly explosive acetone.
“Firefighters surprised the suspect while he was busy opening bottles of acetone,” said Molins.
The blast destroyed part of the hangar and severely damaged the delivery van, a sign, Molins said, of “a significant explosion”.
The headless body of a 54-year-old man, who legal sources told AFP was Salhi’s boss at the delivery company, was found lying near the car along with a knife.
“At an angle not covered by camera his head was hung onto the fence surrounded by two Islamic flags bearing the Shahada, the profession of (Muslim) faith,” said Molins.
He said Salhi, who is in custody, was being probed for murder and terrorism offences.
Salhi’s sister and wife were also being held as well as a fourth person who was suspected of terrorism-related offenses; however his link to the attack was not given.
Molins said “investigations are just beginning” and said investigators were still trying to unravel exactly what happened, how the victim was killed and “if he was decapitated ante-mortem or post-mortem.”
He said they were also focusing on whether Salhi had an accomplice but “there is no sign that allows us to confirm the suspect was accompanied by the suspect in the factory or an accomplice who acted as a lookout before the act was carried out.”
Witnesses said there was only one person in the vehicle.