|The following is based on Fallout Tactics and some details might contradict canon.|
In this encounter, you'll find a group of tribals protecting the border between the United States of America and Canada. Once you come within a certain distance of the group (even if sneaking undetected), the leader beside the camp fire yells, "We don't speak with your kind, Canadian scum! We invaded your country once, and we'll do it again!"
At this moment, the tribals become hostile towards you and will then attack you with an assortment of small guns and melee weapons. The tribal furthest to the northeast carries the unique water gun along with approximately seventy canisters of acid.