The mayor of Muenster says authorities don't yet know the motive behind the van crash that killed three and injured 20 people in his western German city.

Mayor Markus Lewe told reporters that "all of Muenster is mourning this horrible incident. Our sympathy is with the relatives of those who were killed. We wish the injured a quick recovery."

The van crashed into people sitting in front of the famous Kiepenkerl bar on a warm Saturday afternoon in the city's historic downtown.

Police say the driver of the van shot himself to death inside the van after the crash. His identity is not yet known.

Germany's top security official, Interior Minister Horst Seehofer, said federal authorities are in close contact with officials in North Rhine-Westphalia state, where Muenster is located, and all are trying to figure out what happened.