A gun was stolen from a small shop in Wisconsin — it has now been linked to 27 shootings in Chicago.

CHICAGO — With the solid crack of a crowbar, the hooded burglar sent the showcase glass showering onto the gun shop’s floor and quickly swept several pistols into his shoulder bag. Among the cache that New Year’s morning at a northern Wisconsin gun shop was a lightweight 9 mm handgun with a black polymer grip, a black steel slide and a 4 1/2-inch barrel. On one side was the stamp of the handgun’s unique serial number: YZC020. On the other, the logo of one of the most profitable and ubiquitous firearms companies in the world: Glock. The Austrian handgun, a model 17, had been imported to the com...