Story highlights Danielle Jacobs was shot and killed by police in Arizona

Police said she had a knife and that they didn't know she had Asperger's syndrome

(CNN) Danielle Jacobs was public about her struggles with Asperger's syndrome.

Last June, the 24-year-old woman posted a YouTube video of a breakdown in which she wept, berated herself and punched her chest until Samson, her service Rottweiler, jumped up and blocked her blows. Finally, she slumped to the floor and embraced the dog.

Police in Mesa, Arizona, say they didn't know Jacobs had Asperger's, a high-functioning variant of autism , when they shot and killed her Thursday.

Officers went to her home after receiving reports a woman was threatening to kill herself, Detective Estaban Flores said at a Friday news briefing.

Two officers were talking to Jacobs through an open door in the hallway when she emerged and lunged at them with a large kitchen knife, he said.

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