LKS 20170408 dmcf01; This picture taken on April 8, 2017, shows the truck that crashed into the Ahlens department store at Drottninggatan in central Stockholm the day before. Swedish police said on April 8, 2017, that a man arrested on "suspicion of terrorist crime" could be the driver of the truck that ploughed into a crowd of people in a busy Stockholm store department. Sweden had strengthened border controls after an unidentified attacker ploughed a truck through a crowd into a department store in central Stockholm, killing four people and injuring 15. LEHTIKUVA / AFP PHOTO / TT NEWS AGENCY / Maja SUSLIN /