A post has been discovered on the online forum 4chan, which was put up one day prior to the terrorist attack on the Parliamentary estate in London. Apparently the post predicts the attack, in which at least one "alleged assailant" ploughed through a crowd of people and then stabbed and killed a police officer before getting shot by armed police. The post included the attack's exact location, Westminster Bridge, and an Internet-sourced picture of two guns.
Link between poster and attacker is unknown
It is not known at this time what the link between the guy who posted on 4chan and the guy who carried out the terrorist attack on Parliament is, and no outright reference is made in the post to the subject matter of the incident or the date on which it took place (which turned out to be "tomorrow" in terms of the day of posting).
Coordinates in the post, which was posted in 4chan's "Politically Incorrect" posting board, pointed right to Westminster Bridge, specifically the side on which Parliament is located, exactly where the attack took place, around about 24 hours beforehand.