Site of Nice attack
Site of Nice attackReuters

As French authorities delve into the mystery surrounding the Nice truck attack, a Paris prosecutor announced that Mohamed Lahouaiej-Bouhlel had been planning the attack for months, and had accomplices.

Lahouaiej-Bouhlel's friends claim that he showed no signs of radicalization, until a few days before the attack.

Speaking at a press conference today, Prosecutor François Molins explained that despite those claims, pictures and texts on the attacker's phone indicate that he was planning the attack since 2015.

At the moment, France has five suspects in custody for aiding the attack. Molins reported that one of the suspects filmed the scene of the attack the day after. The suspects, four men and one woman, are due to appear in court soon.

Two of the suspects, an Albanian couple, are suspected of supplying Lahouaiej-Bouhlel with a pistol.

Another, aged 22, is believed to have texted Lahouaiej-Bouhlel on the night of the attack, regarding supplying weapons.

Police raided his home, and found a Kalashnikov rifle and ammunition, AFP reports.

ISIS has claimed responsibility for the attack, although the details of the attack are still being unraveled.