Norwegian police said on Monday they had arrested a suspected shooter after receiving reports of gunfire at Oslo's largest shopping centre.
Police said in a statement that no injured people had been found and that it was safe to reopen the centre again, after it was earlier evacuated.
"As of now, it appears that there was only one perpetrator involved," the statement said.
Police spokesperson Tomm Berger told journalists the suspect, a 19 year-old, had called the police before he fired a single shot with a shotgun into the ceiling. The suspect had also been carrying a baseball bat and a knife.

Mediator Pakistan says US, Iran expected to sign initial deal within 24 hours
India Air Force plane crash kills all five onboard
Ukrainian strike kills one, wounds 3 in southern Russia
Trump says US military strike killed leader of Venezuela's Tren de Aragua gang
Qatar rejects media report on energy production decisions
Trump says Iran war deal close as Strait of Hormuz tensions linger
Victims' families mark Air India crash anniversary with prayers and tributes
Ebola outbreak spreads to crowded displacement camp in Congo
