The police responding to the attack encountered firing so intense that they struggled to tell how many gunmen were on the scene, an official said.

Swedish police said they were still investigating the motive behind the country's deadliest mass shooting, as local media began reporting details about the gunman. The suspect, named in reports as 35-year-old local man Rickard Andersson,

Officials in Sweden have vowed to determine why a man killed 10 people, and apparently himself, in an unprecedented attack that's shaken their "society to its core."