French police have taken into custody four family members of Adam Dzaziri, the suspect of the Monday's Champs-Elysees attack, AFP reported citing a judicial source on Tuesday.
The assailant's ex-wife, brother, sister-in-law, and father were all taken into custody on Monday.
The suspect's father told the media that his son "had a registered weapon, and he practiced shooting."
Investigators found a stash of weapons at Dzaziri's home, which included at least nine weapons, such as two pistols, and a Kalashnikov-type assault rifle.
French police said that the assailant had been on a security watch list since 2015.
Dzaziri, a 31-year-old radicalized Islamist, rammed his car into police van near the presidential Palace on Monday and died when the car exploded with weapons and explosives found in his car.
It’s the latest case of terror-related violence in France, which has been under a state of emergency following ISIL shootings that killed 130 people in 2015.