Adam Lanza 4Chan
A copy of the message purportedly posted by Adam Lanza on 4Chan

A 'suicide note' purportedly posted by Connecticut school gunman Adam Lanza on one of the world's most popular online messageboards has been exposed as a fake.

Two messages, apparently taken from social networking site 4Chan, surfaced on the internet in the aftermath of the massacre at Sandy Hook Elementary School which left 27 people dead.

The posts are dated last Wednesday, two days before the shooting, and were supposedly published by an anonymous member. In the first message, the poster writes that "I'm going to kill myself on Friday and it will make the news, be watching at 9am".

When asked by a fellow member where the suicide will take place, the poster responds: "I live in Connecticut, that's as much as I'll say."

The two messages are accompanied by an uncensored picture of the bodies of Eric Harris and Dylan Klebold, who committed suicide after killing 13 people at Columbine High School in 1999.

Several newspapers and websites published the supposed forum posts when they emerged. However, it is now clear that the messages are a hoax.

Although the timestamp on the posts gives the hours and minutes at which they were published, they do not give the seconds - as all genuine 4Chan messages do. Furthermore, the two posts carry serial numbers which were not actually reached by 4Chan until Friday, after the massacre had taken place.

The hoax is the latest in a string of controversies to have blighted 4Chan. The site, founded in 2003, has been linked with the creation of hacktivist group Anonymous, and a group of its members recently attempted to rig Time Magazine's 'Person of the Year' poll to ensure Kim Jong-un finished top.

4Chan has yet to comment on the hoax.