France is awash with illegal firearms transported into the country across porous European borders, it was claimed.
While gun laws are strict, it is not difficult for unauthorised members of the public to get their hands on weapons, according to the president of the Union Francaise des Amateurs d'Armes, a French gun society.
Jean-Jacques Buigne suggested the killer responsible for the attacks outside a school in Toulouse most likely did not have a licence for the heavy calibre .45 automatic pistol he was carrying.
"It's impossible to obtain authorisation for an arm like that if you're not 'clean', if you have any convictions, if you have any history of psychiatric problems," he said.
"It's very complicated to get a weapon like that legitimately. But in France lots of criminals use illegal arms and no law could change that."
He blamed the problem on the open borders between European countries and claimed many arms were carried into France from eastern Europe in vans.
Others have spoken of the difficulty of counting how many firearms there are in the country, with the number estimated at more than three million in 2008.
Many of these were thought to be used for hunting or other sporting activities and the owners of them would have been required to hold a licence.
But it is thought the number of weapons circulating significantly exceeds what official figures suggest.