A gunman opened fire in a Copenhagen shopping mall, one of the largest of its kind in Scandinavia, killing an unspecified number of people and wounding several others Sunday, police said.

The suspected gunman, who is in custody, is a 22-year-old Danish man who was detained near the Fields shopping mall on the southern outskirts of the capital, said police inspector Søren Thomassen, head of the Copenhagen police operations unit.

“We know that there are several dead” and “several injured,” Thomassen told a news conference, adding that terrorism can’t be ruled out. “We do not have information that others are involved. This is what we know now.”

He didn’t provide any further details on the victims or suspect or say how many people were killed or wounded. The shopping center is on the outskirts of Copenhagen just across from a subway line that connects the city center with the international airport. A major highway also runs adjacent to Fields, which opened in 2004.

Images from the scene showed people running out of the mall, and Denmark’s TV2 broadcaster posted a photo of a man being put on a stretcher. Witnesses said people were crying and hid in shops.

Laurits Hermansen told Danish broadcaster DR that he was in a clothing store at the shopping center with his family when he heard “three-four bangs. Really loud bangs. It sounded like the shots were being fired just next to the store.”

Copenhagen Mayor Sophie H. Andersen tweeted: “Terrible reports of shooting in Fields. We do not yet know for sure how many were injured or dead, but it is very serious.”

Police said they were first alerted to the shooting at 5:36 p.m. (1536 GMT; 11:36 a.m. EDT). A huge presence of heavily-armed police officers arrived at the scene, with several fire department vehicles also parked outside the mall.

“One person has been arrested in connection with the shooting at Fields. We currently are not able to say more about the person concerned,” Copenhagen police tweeted. “We have a massive presence at Fields and are working on getting an overview.”

A concert by former One Direction band member Harry Styles was scheduled to be held at 8 p.m. (1800 GMT; 2 p.m. EDT) at the nearby Royal Arena. It was unclear whether the concert would go ahead.

On Snapchat, Styles wrote “My team and I pray for everyone involved in the Copenhagen shopping mall shooting. I am shocked. Love H.”

Shortly after the shooting, the royal palace said a reception with Crown Prince Frederik connected to the Tour de France cycling race had been canceled. The first three stages of the race were held in Denmark this year, the palace said in a statement. The reception was due to be held on the royal yacht that is moored in Sonderborg, the town where the third stage ended.