The man accused of the mass shooting at a supermarket in Buffalo, New York, on Saturday had planned further attacks, police have suggested.
Buffalo police commissioner Joseph Gramaglia said on Monday that the 18-year-old suspect had spoken "about possibly going to another store" after carrying out the shooting at the Tops grocery outlet.
“It appeared that his plans were to drive out of here and then continue driving down Jefferson Avenue, looking to shoot more black people, as he put it.”
“And possibly even go to another store location,” the commissioner told ABC News.
Police in New York state are treating as a racially motivated hate crime the murder of 10 people by a heavily armed gunman at a supermarket in Buffalo on Saturday afternoon.
Police said the gunman shot 11 black victims and two white victims before surrendering.
The suspect, identified in court as Payton Gendron of Conklin, New York, pleaded not guilty on Saturday evening to first-degree murder, a charge that could lead to life imprisonment without parole.
Police believe that the suspect travelled about 320km from his home town near Binghamton in New York state with the intention of carrying out murders in east Buffalo, which has a large black population.
Police are investigating claims that the suspect carried out a reconnaissance mission around the district prior to the attack on Saturday afternoon.
Authorities in New York are also continuing to examine a 180-page document which they believed the suspect in the shooting in Buffalo posted online. This document sets out white supremacist motivations and conspiracy theories. The author describes being inspired by seeing an online video of a 2019 shooting of the Al-Noor Mosque in New Zealand, and by the 2015 shooting at a church in Charleston, South Carolina.
The author of the document expressed admiration for a white supremacist ideology known as replacement theory which claims, baselessly, that white Americans are being replaced by immigrants from abroad.
On Monday, lawyer Ben Crump, who is representing one of the victims in the Buffalo shootings, Ruth Whitfield, said it was important that "we not only hold accountable this individual who committed this hateful act, but we hold accountable those who curate this hate, who radicalise these young white supremacists".
Mr Crump called on officials to define Saturday's attack as an "act of domestic terrorism".
“We can’t sugarcoat it, we can’t try to explain it away talking about mental illness. No, this was an act of domestic terrorism perpetrated by a young white supremacist.”
US attorney general Merrick Garland said the US justice department was investigating the murders in Buffalo as a hate crime and an act of racially motivated violent extremism.
US president Joe Biden on Monday at a ceremony to mark national police week in the US paid tribute to Aaron Salter jnr a retired Buffalo police officer who was working as a security guard at the supermarket on Saturday when the gunman carried out his attack.
Mr Biden said Mr Salter “gave his life trying to save others”.
The president and first lady Jill Biden will visit Buffalo later this week.
US Republican politician Liz Cheney said on Twitter that her party's leadership in the House of Representatives had enabled white nationalism, white supremacy and anti-Semitism.
Separately on Monday, prosecutors in Erie County in New York state said a Buffalo man was facing a charge of making a terrorist threat after calling two businesses in the city and making threatening comments while invoking the killings at the supermarket.