No agreement can be perfect or take all factors into account at the time of negotiations. The normal border guards are from police organisations and are armed with only light weapons, which are rarely brought to use. The army is called in only under conditions of tension and, in case of a skirmish, uses its heavy and destructive weaponry. Under normal conditions, and between friendly countries, the two armies never face each other. Firing between the two border police is rare and, even then, mostly accidental.
Fatalities are even more rare.
In such case, an apology is immediately given and compensation, promptly rendered. The dead are treated with utmost respect and full co-operation is given to the opposite side as far returning the body is concerned. Normal relations between border guards are friendly and they exchange sweets and other speciality eatables on national occasions and festivals. The use of short cuts in remote and inaccessible areas, the result of an understanding between local commanders at a junior level, can become suddenly invalid due to a change in higher level policies or a change in command or regiments, etc. Construction of defensive structures is, often, a very innocuous activity.