Recent immigrants to Europe are predominantly economic migrants, though some are clearly fleeing from war. There are also some who are fleeing the justice in their own countries. A substantial majority are young men.
Unfortunately many come from cultures that condone rape, and expect women to only appear on the streets dressed in a veil. Men from these cultures find it hard to accept that in the West women dress quite differently and that these women are not prostitutes, nor are they inviting sexual assault.
Some buy false papers to make themselves out to be Syrian. Certain NGO's have also encouraged men to claim they are 15, so that they get treated as children even though they are not. This has greatly complicated efforts to extract genuine children from the camps, where they are at risk from some of the older migrants!
In addition, ISIS announced in advance that it would infiltrate those coming to Europe with its members - ready and willing to die for ISIS by terrorising the Western population. Some of the atrocities in Europe have indeed been committed by recent migrants, and hailed by ISIS.