Saturday's shooting in a nightclub and neighboring streets in Oslo, the capital of Norway, resulted in two fatalities and 14 injuries, according to the Norwegian police.
According to authorities, a suspect thought to be the single culprit has been detained.
Police spokesman Tore Barstad told Aftenposten that the crime scene spread from the London Pub to a nearby club and then to an adjacent street, where the suspect was caught a few minutes after the shooting began.
The London Pub is a well-known homosexual bar and nightclub located in the heart of Oslo.
According to local media, three crime scenes have been established.
"I saw a man arrive with a bag, then he pulled out a gun and began firing," NRK journalist Olav Roenneberg recounted.
It was initially unclear what the motivation for the attack was.
Saturday evening will see the annual Pride procession in Oslo.
"Two deaths have been confirmed," tweeted the Oslo police department.
According to the police, fourteen persons were transported to hospitals with severe injuries.
Photographs published by VG, NRK, and others depicted a significant gathering of emergency responders outside the London Pub, including police and ambulance personnel.
Helicopters hovered over the heart of Oslo while ambulance and police car sirens could be heard throughout the city.
The university hospital in Oslo issued a red alert after the incident.
Emilie Enger Mehl, minister of justice, told broadcasters, "This disturbs us all. My thoughts are with the victims and everyone affected. Norway is a community of trust where everyone should feel safe spending a Saturday night outdoors.