DAYTON, Ohio — A woman who was friends with Dayton shooter Connor Betts is speaking out, telling NBC's Today she tried to warn school officials about Betts. 

Lyndsi Doll says Betts confided in him about his mental health problems, even saying he was having trouble sleeping because he feared himself and the voices inside his head.

In the wake of the attack that left nine people dead -- including his own sister dead -- Doll wonders if someone could have stopped him.

“I'm reevaluating the past and wonder what could have been done, whether I could have done something, or someone else could have done something to raise awareness that, hey he's dangerous," she said. "He has history of violence towards women.”

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Doll told Today voices in his head were telling him to hurt others.

“He told me again it was because of his hallucinations, things that he heard whispered to him at night from disembodied voices," she said. "He feared himself, and some nights it was hard for him to sleep.”

So far, investigators have not been able to determine a motive behind the attack.

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