A man was arrested in northern Stockholm after four people were killed and 15 injured when a truck plowed Friday into shoppers on the Drottninggatan Street of Stockholm. Prime Minister Stefan Lofven says it was almost certainly a terror attack. An image was released of the suspect wearing a hooded jacket, who was seen fleeing toward a nearby subway station. Police shut down the entire underground system for the manhunt. The suspect earlier hijacked the truck from the Swedish beer maker Spendrups, while its driver was unloading a delivery at a restaurant. The driver was not injured. Helsinki police have tightened security measures at the center of the Finnish capital. Traffic via Orseund Bridge between Sweden and Denmark was also partially limited at the request of Swedish police.