Why We Wrote This New Year’s Day attacks show a changing threat matrix for U.S. cities, amid the rising use of vehicles as weapons, a seemingly expanding set of domestic and international grievances, and the embrace by some Americans of political violence. The New Orleans attack is being investigated as an act of terrorism, and the FBI said it is working through a Joint Terrorism Task Force to determine if the Las Vegas explosion was an act of terrorism, The Washington Post reported. A recent study found that vehicle-ramming attacks have increased since 2010, with over 60 attacks in cities including London, New York, Berlin, and now New Orleans, acts that killed over 240 people and injured more than 1,000.