A new suspect is in custody Friday in the investigation into a gruesome attack by a Tunisian man who killed three people in a French church, as France heightened its security alert amid religious and geopolitical tensions around cartoons mocking the Muslim prophet.

The suspect is a 47-year-old man believed to have been in contact with the attacker the night before the attack on the Notre Dame Basilica in the Riviera city of Nice, according to a judicial official. The official was not authorized to be publicly named.

The attacker, Ibrahim Issaoui, was seriously wounded by police and hospitalized in life-threatening condition, authorities said. Anti-terrorism prosecutors in France and Tunisia are investigating.

In an interview broadcast Friday with Saudi-owned Al-Arabiya TV, Issaoui’s mother said she was shocked by the events.

From the Tunisian province of Sfax, the mother, her eyes wet with tears, said she was surprised to hear her son was in France when he called upon his arrival and had no idea what he was planning. “You don’t know the French language, you don’t know anyone there, you’re going to live alone there, why, why did you go there?” she said she told him over the phone at the time.

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His brother told Al-Arabiya that Issaoui had informed the family he would sleep in front of the church and sent them a photograph showing him at the cathedral where the attack took place. “He didn’t tell me anything,” he said. A neighbour said he knew the assailant when he was a mechanic and held various other odd jobs and had shown no signs of radicalization.

France’s anti-terrorism prosecutor said the suspect is a Tunisian born in 1999 who reached the Italian island of Lampedusa, a key landing point for migrants crossing in boats from North Africa, on September 20 and travelled to Bari, a port city in southern Italy, on October 9. It is not clear when he arrived in Nice.

The attack was the third in less than two months that French authorities have attributed to Muslim extremists, including the beheading of a teacher who had shown caricatures of the Prophet Muhammad in class after the images were re-published by satirical newspaper Charlie Hebdo.

President Emmanuel Macron said he would immediately increase the number of soldiers deployed to protect schools and religious sites from around 3,000 to 7,000.