The man suspected of decapitating his boss in an attack on a gas factory in France has confessed to the grisly crime, sources close to the investigation said on Sunday.Yassin Salhi, 35, “has also given details about the circumstances” surrounding the killing, according to the sources, who said he would be transferred to Paris for further questioning later on Sunday by anti-terrorist police.Salhi’s confession came after it emerged the married father-of-three sent a gruesome selfie photo of himself and the severed head to a WhatsApp number in Canada.