Police say a 30-year-old Ukrainian national from Donetsk has been identified as the suspect in a mass stabbing incident in Amsterdam . Five people were left injured when a man began stabbing people at random in Dam Square on Thursday . It included two people from the United States, one from Belgium, and one from Poland . The attack lasted several minutes before the assailant was stopped by a 'heroic' British tourist and arrested. Police cordoned off the area, and several ambulances and a trauma