The French beheading attack suspect who decapitated his boss, took a selfie with the dead body, sent the photo to a friend via whatsApp and then attacked and caused an explosion at a chemical factory has admitted the crime, but authorities are still investigating his motives.

Yassin Salhi, a deliveryman, told investigators that he killed his boss because of personal issues related to work and family, according to The Guardian.

He told police that he killed Herve Cornara in a parking lot before going to the chemical plant in Saint-Quentin-Fallavier, 30 kilometers away from Lyon. French media described Salhi as being seemingly confused while police questioned him about his motive for the murder and the factory attack.

Salhi told authorities he wanted to kill himself after murdering his boss. He said his attack at the chemical plant, which was made to look like a terrorist attack, was meant to cap his success, The Guardian reported.

However, authorities are investigating other possible motives, as they discovered a phone from Salhi's friend in Syria who was one of the recipients of the photos Salhi sent. According to reports, the friend told relatives that he would ask ISIS for permission to propagate the photos, CNN reported.

Paris prosecutor Francois Molins said investigations will look into Salhi's ties with terrorism-related activities.

"The beheading, the sinister staging, the willingness to provoke an explosion in a sensitive site, sending pictures as a trophy for his crime to a correspondent in Syria - all this causes a shock, which of course gravely disturbs public order through intimidation and terror," he said.

Molins said Salhi's photos may have been intended for ISIS' social media propaganda campaign.

The French prosecutor said a phone from Sebastien Younes, another friend of Salhi who has been staying in Syria since November last year, was also a recipient of the photos sent from Salhi's phone. After confirming he received the photos, Younes reportedly asked permission from ISIS to disseminate them, CNN reported.

Investigations revealed that Salhi convinced his boss to go inside the minivan he was driving, where Salhi knocked him unconscious with a tire jack and strangled him. Salhi then beheaded him before reaching the chemical factory. Investigators are not sure if Cornara was already dead at the time of beheading.

Salhi rammed his van into a warehouse at the factory and caused an explosion. Firefighters who responded to the incident found Salhi attempting to open acetone canisters while shouting "Allahu Akbar." They found Cornara's head tied on a fence along with two flags with the Islamist profession of faith.

"According to him his motive was only personal and not terrorist," Molins said. "One does not exclude the other."

Molins pointed out Salhi's desire for publicity. "He decapitated his victim, he hung the head on a chain and he wanted to get the maximum publicity possible," he said, according to CBS News.

"This corresponds very precisely to the orders of Daesh [Isis] which calls regularly for acts of terrorism on French soil and in particular to cut the throats of unbelievers," Molins said, according to another report from The Guardian.