Due to my personal experience, it can be due to medication, that totally changes a persons mental state.
My great uncle 5 years last month committed suicide. He got up, had a shower, had breakfast, my great auntie went to have her shower, he went into the garage, with no explanation and killed himself. i wont say how. My auntie found him, and we still don't know to this day. And BELIEVE me! This man was the biggest laugh going, joking around, always smiling!
Forensic analysis revealed that the type of "cant remember the name of it"medication had side effects of mental instability and depression!!
Im not saying its the same, there is one thing to take your own life, and the lives of many others, its a totally devastating story, and i cant remember what that town is like down their with the situation.
But it may be a similar diagnosis, i have seen 2 incidents since, that i cant specifically recollect that are down to the same reasoning.