The bombing limited much of the leniency the Swiss had shown toward Allied airspace violations. Eventually, the problem became so bad that they declared a zero-tolerance policy for violation by either Axis or Allied aircraft and authorized attacks on American aircraft. Victims of these mistaken bombings were not limited to Swiss civilians but included the often confused American aircrews, shot down by the Swiss fighters as well as several Swiss fighters shot down by American airmen. In February 1945, 18 civilians were killed by Allied bombs dropped over Stein am Rhein, Vals, and Rafz. Arguably the most notorious incident came on 4 March 1945, when Basel and Zurich were accidentally bombed by American aircraft. The attack on Basel's railway station led to the destruction of a passenger train, but no casualties were reported; a B-24 Liberator dropped its bomb load over Zürich, destroying two buildings and killing five civilians. The crew believed that they were attacking Freiburg in Germany. As John Helmreich points out, the pilot and navigator, in choosing a target of opportunity, "missed the marshalling yard they were aiming for, missed the city they were aiming for, and even missed the country they were aiming for".