Europeans discover that the continent is not made of magic dirt that assimilates migrants into your society upon entry.
Europeans also discover that weapons restrictions only go so far when you have active organized criminal groups with the initiative and contacts necessary to smuggle firearms and grenades into Western/Northern Europe from a number of regions (Ex-Yugoslavia, Albania, former Soviet Union, North Africa, etc.) that are only a car-ride or fishing boat trip away.
Europeans also discover that weapons restrictions only go so far when you have active organized criminal groups with the initiative and contacts necessary to smuggle firearms and grenades into Western/Northern Europe from a number of regions (Ex-Yugoslavia, Albania, former Soviet Union, North Africa, etc.) that are only a car-ride or fishing boat trip away.