French television has obtained video footage of the suspected Islamist militant shot dead by police at the weekend.
33-year-old Jeremie Sidney is believed to have carried out a grenade attack on a Jewish supermarket in Paris last month.
12 suspected radical Islamists were arrested in a nationwide anti-terror operation at the weekend.
The youngest was 18-year-old Yann Nsaku. The former youth footballer for the English side Portsmouth was detained in the city of Cannes.
Nsaku’s brother has told French TV that he was allegedly threatened by the dead suspect Sidney.
“He said if I continued to influence my little brother and turn him against Islam. He said I should be in no doubt that he and his Muslim brothers would come after me.”
Sidney was shot dead during an exchange of gunfire with officers at his home in the eastern city of Strasbourg.
Investigators says he had spent two years in jail for drug offences and had turned to radical Islam while inside.
Police say they have evidence that those detained where preparing other attacks on France’s Jewish community.
They can be held for 96 hours without charge.