The man suspected of shooting dead 10 people at a supermarket in Buffalo, New York, deliberately sought a site with a high black population, authorities say.
The suspect, Payton Gendron, 18, drove more than 320km (200 miles) to carry out the attack, police say.
The attack is being investigated as an act of racially motivated violent extremism.
Buffalo Mayor Byron Brown said the suspect arrived intending to take “as many black lives as possible”.
A 180-page document seemingly authored by Mr Gendron has emerged, in which he describes himself as a fascist and a white supremacist.
