A gunman opened fire in Oslo’s night-life district early Saturday, killing two people and leaving 10 seriously wounded in what police are investigating as a possible terrorist attack during the Norwegian capital’s annual Pride festival.

The shootings happened around 1 a.m. local time, sending panicked revelers fleeing into the streets or trying to hide from the gunman. Investigators said the suspect, identified as a 42-year-old Norwegian citizen originally from Iran, was arrested after opening fire at three locations in downtown Oslo.

Olav Roenneberg, a journalist from Norwegian public broadcaster NRK, said he witnessed the shooting. “”I saw a man arrive at the site with a bag. He picked up a weapon and started shooting,” Roenneberg told NRK. “First I thought it was an air gun. Then the glass of the bar next door was shattered and I understood I had to run for cover.”

Organizers of Oslo Pride canceled a parade that was set for Saturday as the highlight of a weeklong festival. One of the shootings happened outside the London Pub, a bar popular with the city’s LGBTQ community, just hours before the parade was set to begin.

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