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".

Police believe the suspected killer - identified by a Reuters source and Swedish media as Rickard Andersson, a 35-year-old unemployed recluse - acted alone in Tuesday's attack on an educational campus in Orebro, about 200 km (125 miles) west of Stockholm.

Swedish police found three rifles near the body of the gunman, who they believe took his own life.

"The police who arrived at the scene have spoken about what could be described as an inferno ... dead people and injured people, screams and smoke," Orebro police chief Lars Wiren said.

Police found 10 empty bullet magazines and a "large amount" of unused ammunition. Wiren said police arrived on the scene five minutes after the alarm was raised and believed the attacker then began directing his fire towards them.

"After approximately one hour, the acute operation was over when the suspected perpetrator was found dead with several weapons near him," Wiren said, adding that police had not opened fire during the incident.

Police said the smoke was not caused by fire but by "some sort of pyrotechnics". Several police had to seek medical attention for inhaling smoke.