Austria's cases in recent weeks have surged well past the levels recorded in the spring, forcing the government to impose a curfew between 8 pm and 6 am starting Tuesday until the end of November.
The attacks, in six locations including near a synagogue in the centre of the city, were carried out by "several suspects armed with rifles", police said on Monday night.
It is unclear exactly how the headdress, made of hundreds of long quetzal feathers and more than 1,000 gold plaques, ended up in Austria, where it is on display at a museum in Vienna.
