What happened in the United States is not an American tragedy only. It is a tragedy, a lesson and a cause for thought for the entire humanity,` said Bulgarian President Petur Stoyanov at a meeting with 400 firefighters from throughout the country in connection with the Firefighters` Day. `When we speak of your difficult and worthy work, we cannot but mention the terrorist acts in New York and Washington,` said Stoyanov. He described terrorism as the biggest threat for humanity after World War II. `Terrorism can disturb the world even more than a war can because, no matter how disgusting a phenomenon war is, it nevertheless submits to certain rules,` said Stoyanov. Terrorism, in his words, is an extremely vile phenomenon, which hits one in the back, and innocent people fall victims.