A transgender man who had Asperger's syndrome has been shot dead by Arizona police officers who had been called to his home after neighbours reported he may be about to commit suicide.

The police report claim that the officers fired after Kayden Clarke approached them with a knife. Clarke's mother Stacia has already condemned the police department stating that the shooting was unnecessary, saying Clarke had mental health issues.

"They shot and killed a 24-year-old autistic, mentally ill individual whom they had been familiar with and aware of her special needs," Stacia told the Daily News.

Clarke had gained fame last year after posting a series of videos to YouTube documenting his transition from male to female and showing his dog preventing him from self-harming during anxiety and panic attacks. In one video, which is now set to private and cannot be viewed, shows Clarke's Rottweiler Samson stopping him self-harming. The dog had been trained to block Clarke's attempts to hurt himself using his paws.

A spokesperson for Arizona's Mesa Police Department confirmed that the officers had discharged their weapons when Clarke came at them with a knife. "She had one knife that we know of, she had something else we're not sure what it was – the officers said it was dark inside the room. When she made contact with them she approached them with the knife, extended it out, and they felt threatened."

The officers have said they fired in self-defence. None of the officers were hurt in the incident, but they have now understood to have been placed on administrative leave from the Mesa Police Department.