A man went to sleep and he turned off the light. The next day when he woke up to many dead people, due to his actions the night before. How come?

There is a grand prize of 0.003 SBD for the winner and two 0.001 SBD runner up prizes.

The winner is chosen randomly out of all correct answers after 7 days as well as the runners up. I will use a random number generator and assign numbers to all answers, first number chosen is the winner, next two are runners up. (It's a small prize but mainly just for fun.)

Please optionally upvote if you like this post or give an answer, have fun!

I usually, but not always, get voting bots on my posts after a few days to allow people to earn curation rewards.