What we know so far about the Buffalo mass shooting

People pray outside the scene of a shooting at a supermarket, in Buffalo, N.Y., on Sunday. A day earlier, a white 18-year-old killed 10 people and wounded three in what authorities described as "racially motivated violent extremism." (Matt Rourke / AP)

A white, 18-year-old gunman allegedly carried out a racist attack at a supermarket in Buffalo, N.Y., on Saturday, killing 10 people and injuring three others, according to authorities. Almost all of the victims were Black. The suspect, who livestreamed the mass shooting, is believed to be the author of a screed posted online detailing his white supremacist ideologies and his plan to target a Black community in New York.

Here's what else we know.