Sweden is reeling from the country's deadliest mass shooting this week as investigators continue to look into the gunman's motive.

A gunman opened fire at an adult education center in the Swedish city of Örebro on Tuesday, killing at least 10 people in what the country’s prime minister called the “worst mass shooting in Swedish history.

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