Terrified revellers at a gay bar in Oslo hid in a basement and desperately called loved ones as a gunman went on the rampage, killing two people and injuring more than 20 on the day the city was due to celebrate its annual Pride parade.
The attack took place in the early hours of Saturday, with victims shot inside and outside the London Pub, a longstanding hub of Oslo's LGBTQ scene, as well as in the surrounding streets and at one other bar in the centre of the Norwegian capital.
Bili Blum-Jansen, who was in the London Pub, said he fled to the basement to escape the hail of bullets and hid there along with 80 to 100 other people.
"I had a bit of panic and thought that if the shooter or shooters were to arrive, we'd all be dead. There was no way out."
A suspect, a 42-year-old Norwegian citizen of Iranian origin, was detained minutes after embarking on the shooting spree, according to police who said they believed he acted alone.
Two weapons, including a fully automatic gun, were retrieved from the crime scene, they added.
"There is reason to think that this may be a hate crime," police said.
"We are investigating whether the Pride was a target in itself or whether there are other motives."
The suspect, who was known to authorities, is believed to be a radicalised Islamist who has a history of mental illness, Norway's PST intelligence service later said.
Other witnesses described the chaos that erupted inside and outside the London Pub, which has been open since 1979.
"My first thought was that Pride was the target, so that's frightening."
Journalist Olav Roenneberg of public broadcaster NRK said he was in the area at the time and saw a man arrive with a bag, take out a gun and start to shoot.
"Then I saw windows breaking and understood that I had to take cover," he said.
Authorities said that the attack was also being investigated as a possible act of terrorism and said they did not rule out mental illness being a factor.
'We're here, we're queer, we won't disappear'
Norwegian police, who are not normally armed, will now carry guns until further notice as a precaution, national chief Benedicte Bjoernland said.
Norway's PST intelligence service added that it was investigating whether there could be further attacks but that currently there was no indication of that.
The organisers of Oslo Pride cancelled Saturday's parade, citing police advice.
"We will soon be proud and visible again, but today we will mark Pride celebrations at home," they said.
Still, several thousand people began what appeared to be a spontaneous march in central Oslo, waving rainbow flags and chanting in English: "We're here, we're queer, we won't disappear."
Prime Minister Jonas Gahr Stoere said in a Facebook post that "the shooting outside London Pub in Oslo tonight was a cruel and deeply shocking attack on innocent people."
He said that while the motive was unclear, the shooting had caused fear and grief in the LGBTQ community.
The shooting took place just months after Norway marked 50 years since the abolition of a law that criminalised gay sex. The suspect was known to authorities, including for violence of a less severe nature, police said.
The Nordic nation of 5.4 million has lower crime rates than many Western countries, though it has experienced hate-motivated shootings, including when far-right extremist Anders Behring Breivik killed 77 people in 2011.
AP/Reuters