An 18-year-old white gunman shot 10 people to death and wounded three others at a grocery store in a Black neighborhood of Buffalo, New York, before surrendering after what authorities called an act of "racially motivated violent extremism."

Authorities said the suspect, who was armed with an assault-style rifle and appeared to have acted alone, drove to Buffalo from his home several hours away to launch a Saturday afternoon attack that he broadcast in real time on social media platform Twitch, a live video service.

Eleven of the 13 people struck by gunfire were Black, officials said. The two others were white. The racial breakdown of the dead was not made clear.