premise: Trains, trams, cars and buses ground to a halt on Monday after a shoot-out between 18:00 CET and 19:00 CET in the historical city of Basel in Switzerland. The first shots were fired at around 16:00 CET according to the spokesperson of the Government. Special Police Forces were getting prepared to launch an assault against this building. The authors of the shoot-out are unknown as well as their target. Railway traffic was blocked off at around 18:00 CET, according to the Swiss Federal Railways' (SBB-CFF-FFS) spokesperson, Christian Kräuchi. At around 19:00 CET, railway traffic resumed.
hypothesis: Basel is a European city.