There was once a recluse who never left his home. The only time anyone ever visited him was when his food and supplies were delivered, but they never came inside. Then, one storm winter night when an icy gale was blowing, he had a nervous breakdown. He went upstairs, turned off all the lights and went to bed. Next morning, he had caused the deaths of several hundred people. How?
(the other day at acro we were trying to remember what this riddle was... well i found it on a google search.)