The man – born in Nancy, eastern France – was put under formal investigation on suspicion of terrorist association with a view to perpetrating a crime, the prosecutor’s office said in a statement. He “knew very well, if not of the exact place or time, of his cousin’s impending plans for violence”, the statement said.
In a related development, the prosecutor’s office said another man identified has been charged for attepmpting to reach Syria last month with one of the two French priest’s killers.
Knife-wielding attackers interrupted a church service in Saint-Etienne-du-Rouvray, western France, on July 26, forced 85-year-old Roman Catholic priest Father Jacques Hamel to his knees and slit his throat.
Police identified a 19-year-old local man as one of the attackers. He had made failed bids to reach Syria to wage jihad, wore an electronic tag and was awaiting trial for alleged membership of a terrorist organisation, having been released on bail.
They identified the second attacker as Petitjean, also 19.
Both were shot dead by the police.
Investigators are trying to determine how the two men met.
Le Parisien daily newspaper reported on Sunday they had held a conversation on July 22 on the instant messaging service Telegram.
A Syrian asylum seeker thought to be linked to the church attack, and who had been arrested last week, was released on Sunday, a source close to the investigation news paper agencies