Other forms: looters
Someone who takes advantage of a chaotic situation to steal things is a looter. During a war (or even during a blackout), looters may help themselves to food and supplies from shops.
When you think of a riot, you probably not only imagine angry people shouting in the street and damaging property, but also looters raiding stores and stealing goods from them. Looter, defined in the 1850s as "one who plunders," comes from loot, "to steal," from the Hindi lut and loptram or lotram, "stolen property," in Sanskrit.