The German newspaper Bild claimed its reporter Axel Lier witnessed the helicopter crash during a federal police training exercise. He told the newspaper everyone was "totally shocked" by the incident.
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The Ukip leader hits out at Douglas Carswell after reportedly only finding out about the MP's blog post resignation in a text from a friend.
Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.
The violence began after a counter-protester allegedly doused a female rally organiser with pepper spray.