School is closed!

Last night at about midnight, a 16 year old student at Halden's Secondary school caused it to close for the whole of today. How?
Yodel is an anonymous app, that lets you write a short message to a very  localised feed, so only people near you will see it (e.g. in Halden). Users can upvote or downvote the message, 5 downvotes and they disappear. This boy wrote "An upvote and I shoot up the school". For obvious reasons when this was reported to the police they took it very seriously indeed, all students and staff were sent an sms at 06:30 telling them the school was closed due to a threat.
You can read more here