Det. Esteban Flores of the Mesa Police Department tells PEOPLE that officers were dispatched to the home of Kayden Clarke (born Danielle Jacobs) on Thursday after friends claimed he'd threatened suicide in emails and text messages.
A video Clarke posted on YouTube last year went viral as it showed how his dog, Samson, assisted him during his struggles with Asperger's. (The video has since been removed but versions of it were re-uploaded on YouTube.)
Flores says that friends helped police enter Clarke's home, where officers tried to make contact with him.
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"The officers were in a small hallway that leads into the bedroom," Flores explains. "The door was open and it was dark; there were no lights on."
Clarke then appeared in the bedroom doorway, brandishing a 12-inch kitchen knife, says Flores. Clarke allegedly refused to drop the knife, and instead lunged at the officers, Flores tells PEOPLE.
"They fired their weapons and unfortunately, [he] went down," Flores says.
In a video posted online in December, Clarke discussed beginning gender transition therapy, expressing excitement that his insurance would cover it.
The two officers, who have not been identified, are now on administrative leave, Flores confirms.