What is non binary? And was there more than one person killed in that bathroom?
You're not allowed to ask those questions.
"Non-binary" means that the person identifies himself or herself as neither, or not solely, male or female. Like any other form of transgender identity, it has no objective existence. There is neither a spectrum of gender between male and female, nor is there any third sex that would not fall along that spectrum.
Non-binary people frequentliy use they/them pronouns (i.e. request or demand that
other people use they/them pronouns when conversing about them). The rationale is that "they" or "them" is the "gender-neutral" pronoun in English. This is only partly true: in recent decades those pronouns have largely replaced the generic "he" when speaking of persons of unspecified quantity or sex. However, Nex Benedict was one person having a known sex. She's a she.
This leads to some linguistic confusion, as in this particular case, in which a non-binary person was in a fight with a group of people. Both parties use plural pronouns, making it difficult to write coherent sentences in which you can tell them apart. It also leads to confusing sentence constructions like: "Nex Benedict
was a nonbinary child. They
were beaten, viciously in a high school bathroom of Owasso High School." "Were" is a plural verb. There was one of her.