From the Washington Post article about the Swedish truck massacre:
"The police did not give any details about the man. But the Swedish newspaper Aftonbladet reported that he is a 39-year-old from Uzbekistan, and is a supporter of the Islamic State."
“There is no way to really prevent this kind of thing,” said Stefan Hector, an official with Sweden’s national police.
You might try importing fewer young males from unstable Islamic countries. Why exactly does Sweden need young Uzbek males?