well, it was before i got there, but a science teacher from my first high school tried to kill a bunch of people by opening all the valves on the bunsen (spelling?) burners and leaving both doors to the room wide open. there was some event (think it was graduation, but i cant remember the story completely) that evening, and since school was closed that during the day, he had several hours to let the gas spread. fortunately, the resource officer was there and smelled something funny (good god, thats one dark unintended pun...damn), and found the source.
totally leaving out some details, but its been forever since i had heard or even thought about it. forgot whether he wanted to off himself with it as well or if there was a bomb or other timed device to ignite it. either way, the plan got shut down, and its a pretty good bet that he's in a psychiatric institute somewhere.