Andres Sacopla - goes on a shooting because his lunch box is missing

Interesting case I found on Amok Wiki.

Andres Sacopla was a Filipino farmer who killed eight people and wounded two others in Cabayugan, a village in Pangasinan Province, Philippines on September 4, 1972.

Sacopla, who was described as well-behaved, became despondent and irritable due to the hardships caused by month-long floods in July the same year. On the aforementioned date the 48-year-old left his buffalo in a paddy, and upon return found his lunch box missing. Suspecting that it was stolen by a neighbour, Sacopla went home, armed himself with a shotgun, and began shooting people. He was eventually cornered in an abandoned house by a village official, who grabbed his gun and fatally hit him on the head.

Original: Amok Wiki