This isn't a cosplay competition that got out of hand. Rather, Japanese zoo staffs train intensively to capture animals that may escape in the confusion and destruction of earthquakes. They use people dressed as animals, such as this zebra and this rhinoceros, to simulate the animals.
Most recently, a zoo put a woman in a gorilla costume and had her escape from confinement. Although I can't find the gun in the video, they appear to shoot her with a tranquilizer dart, then wrap her with nets.