US President Joe Biden has condemned white supremacy as “a poison running through our body politic” during a visit to Buffalo, New York.
Ten black people were killed at a supermarket in the city on Saturday in what is believed to be a racially motivated hate crime.
The suspect, 18, identified himself as a fascist and white nationalist in a document posted online.
Mr Biden on Tuesday said the young man belonged to “a hateful minority”.
After meeting families impacted by the shooting, he eulogised the victims for their “individual lives of love, service and community that speak to the bigger story of who we are as Americans”.
“White supremacy will not have the last word,” he said.
Local officials say the alleged attacker drove more than 320 km (200 miles) to deliberately seek out an area with a high black population. He would have continued to target other such areas if he had not been stopped, according to investigators.
In his so-called manifesto, he referenced “white genocide” and “white replacement” conspiracy theories to explain his resentment towards minority groups. In the rambling screed, he also identified politically as being on the “authoritarian left”.
