Poor girl. Could have happen to anyone though. Migrant or not. The way I see it the guy is a sick psycho. It has nothing to do with him being a migrant or not. Could be your neighbour, your uncle or anyone going on a killing spree. One of my friends is a psychologist working in a French jail with murderers. A psycho can easily click and kill someone on instinct. Statistically speaking, the chance of having psychos among migrants is the same as ours. The only difference is maybe those with post traumatic stress, war experience and terrorists / fanatics.
But those should not get allowed in Sweden tbh. Isn't there some kind of interview with a psychiatrist to check on them upon arrival?
This article suggest this Nuur was sick or a potential terrorist lying about his identity.