https://www.pcgamer.com/fortnite-update-v520-rolls-out-double-barrel-shotgun-and-steady-storm-ltm/

Patch notes for Fortnite's update v5.20 have landed, and, yes, they come with the double barrel shotgun. 

"Devastating at close range, the Double Barrel Shotgun packs a punch with each of its 2 shots," says this post of the Legendary and Epic variant weapon that can be found in floor loot, chests, Supply Drops and Vending Machines. Said to deliver a "high burst damage" up close, the twin shooter's power expectedly tapers off at distance.