In human terms, when one of our primitive ancestors first picked up a stick or a stone in anger. If you include the animal kingdom, perhaps snakes which spit venom, skunks which emit foul-smelling repellent and other such creatures might be said to be using 'weaponry' too.
Certainly in Paleolithic (Old Stone Age) times, Early Homo Sapiens used stone tools and weapons, and upright-walking man-apes such as Australopithicus (4MYA) would no doubt have used sticks and thrown stones, because it is known that modern apes do this.