Most deadly Islamist terrorist attacks ever in France followed months of warnings from French officials . The threat of a terrorist attack in the EU is greater than at any time since 2000 , he said . Support for ISIS runs deep among French immigrant communities .
Most deadly Islamist terrorist attack ever in France followed weeks of warnings from French officials . The threat of a terrorist attack in the EU is greater than at any time since 9/11 , officials say . Support for ISIS runs deep among disenfranchised immigrant communities .