The shooter who earlier this week killed 10 people in Sweden’s worst mass shooting was connected to the adult education center where he opened fire with at least one rifle-like weapon, law enforcement officials said Thursday.

A gunman who killed 11 people, including himself, at an adult education centre in central Sweden may have been a student at the school, police said on Thursday, as they described chaotic scenes after the country's deadliest mass shooting as being like an "inferno".

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."