Police say a Canterbury University student is extremely apologetic after writing a letter threatening to use an automatic weapon in the student library.
The letter was published in the university's magazine five weeks ago, but a complaint on Friday brought the matter to police attention.
Police spokesperson Ken Carter says the letter writer contacted police on Tuesday and apologised, saying he had no idea it would have such ramifications.
Mr Carter says the person is not considered a risk to the public and no further action will be taken.
The university's student association earlier described the letter as flippant and stressed it should be kept in context.