“Cautious all-clear. We have found a person, who had committed suicide. He appears to be culprit and to have acted alone.”

Chief of staff Peter Altmaier said that chancellor Angela Merkel was being “constantly briefed” on developments in Munich and will convene the German security council on Saturday in Berlin.

Police warned locals to leave the city center and stay home, and asked that people refrain from posting pictures or videos of the police operation. They described the incident as an “acute terror situation” (link in German).

“We assume it’s a terror attack so that we can ensure maximum resources and measures,” explained Munich police spokesman Marcus Martins, according to the BBC. ”If it turns out that there is a completely different background to this, then we certainly mobilized a lot of resources but we had a worst-case scenario covered.”

The shooting began in the Olympia shopping center in the northwestern Moosach district at around 6pm local time. Police have since cordoned off the area surrounding the shopping center, adjacent to the Munich Olympic stadium. The central station has been evacuated and all regional and city train lines closed.

On news of the shooting, US president Barack Obama said “our hearts go out to those who may have been injured” and pledged support to Germany.

In a statement, German president Joachim Gauck expressed “horror” at the attack. “My thoughts are with all the victims, and all those who are mourning for or worrying about loved ones,” he said.

German interior minister Thomas de Maizière was on his way to the US, but will return immediately.

Facebook has activated its safety check for Munich, and Twitter hashtag #Offenetür (open door) has been set up by locals offering shelter to people unable to get home. Islamische Zeitung, a Muslim newspaper in Germany, said Munich’s mosques will stay open to welcome people who need shelter overnight.

Germany has been on high alert since a young man wielding an axe attacked passengers on a train in Bavaria on Monday, seriously wounding several.

This post was updated at 9:05pm ET.

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