Looting.
See the Wikipedia article on Looting, specifically in cases of catastrophe, sense (1) natural disaster.
Quoting from Wikipedia:
Looting, also referred to as sacking, ransacking, plundering,
despoiling, despoliation, and pillaging, is the indiscriminate
taking of goods by force as part of a military or political victory,
or during a catastrophe, such as war, natural disaster, or
rioting. The term is also used in a broader sense to describe
egregious instances of theft and embezzlement, such as the
"plundering" of private or public assets by governments. Looting
is loosely distinguished from scavenging in terms of objects taken:
scavenging implies taking of essential items such as food, water,
shelter, or other material needed for survival while looting implies
items not necessary for survival such as luxury goods, art work,
precious metals or other assorted items of value to the looters. The
proceeds of all these activities can be described as loot, plunder,
spoils, or pillage.
Looting during a riot or a natural disaster is deemed a despicable act and historically (as recently as the 2005 hurricane Katrina in New Orleans) in the United States there have been occasions when it has been sanctioned for police or even civilians to "shoot looters on sight." See http://www.volokh.com/posts/1125599174.shtml
opportunistic looting