A white supremacist teenager who shot dead 10 people at a supermarket in Buffalo, New York, singled out Sadiq Khan, the Mayor of London, as a target in a hate-filled manifesto posted online. Payton Gendron, 18, was arrested at the scene of the shooting – one of the deadliest racist attacks in recent US history – in a predominantly black neighbourhood of Buffalo on Saturday night. Eyewitnesses outside the Tops market on Buffalo’s East Side told The Telegraph they saw a racial slur scrawled on the gunman’s weapon. He killed 10 people and injured three , most of them black....