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 have said.
The suspect, an 18-year-old white male, drove more than 320km (200 miles) to carry out the attack, police said.
The attack was 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 the alleged attacker, Payton Gendron, has emerged, in which he described himself as a fascist and a white supremacist.
Questions were being asked about how he was able to carry out the shooting when concerns had already been raised. “I want to know what people knew and when they knew it,” New York Governor, Kathy Hochul, told ABC News.
Joseph Gramaglia, Buffalo’s chief of police, told reporters the gunman had made “generalised threats” while still at high school. He spent a day and a half in hospital undergoing a mental health evaluation, but was then released.
Police believed that he planned to “continue his rampage”following the attack had he not been stopped, Mr Gramaglia told CNN, with evidence suggesting that he had plans to target a second store.
He did not appear to have remained under watch by authorities.
FBI Special Agent, Steven Belongia, told the New York Times neither state police nor the FBI had any intelligence on the alleged attacker.
Meanwhile, the gun store owner who sold him a semi-automatic weapon told several US outlets that no alert came up when his name was run through a government background check system.
Meanwhile, New York’s Attorney General, Letitia James, said her office would focus on extremist material online.
“This event was committed by a sick, demented individual who was fuelled (by a) daily diet of hate,” she said.
The shooting has stunned the local community. One of those attending a vigil on Sunday told Reuters: “It just hurts, why would somebody do that.”
Of the 13 people shot, police said 11 were black. Among those reported killed were a man buying cupcakes for his son’s birthday and a woman who had gone shopping after visiting her husband at a nursing home. –CNN/Reuters
