Danielle Jacobs pictured with her Rottweiler Samson. Police shot her dead yesterday after she allegedly attacked an officer with a knife in a suicidal episode

A woman who warmed the hearts of the world with a touching video of her dog helping her cope with Asperger's syndrome has been shot dead by police.

Danielle Jacobs' video showed her having a meltdown and trying to punch herself, but Rottweiler Samson came to her aid and parried the blows with its paws.

Police say they visited her home in Mesa, Arizona, yesterday at 11am over concerns she was attempting to commit suicide, and were forced to open fire when she attacked officers with a knife.

Her mother, Stacia, who is in her 70s, claims that the shooting was not necessary and said her daughter seemed fine when she had spoken to her the day before.

She told The Daily News: 'Before the police arrived she wasn't posing a threat to the community at all. And the police came into her own place.

'They shot and killed a 24-year-old autistic, mentally ill individual whom they had been familiar with and were aware of her special needs.'

Mesa Police Department had responded to another suicide call in the same home - an apartment next to her parents' - two years ago, Detective Esteban Flores told AZ Family.

The shooting is less than a year after Jacobs bravely filmed herself being comforted by her service dog during a depressive episode to raise awareness about the disease.

She wrote 'This is what having Asperger's is really like' as she posted the footage of the intensely personal moment on her YouTube channel in June last year.

In the clip, her loyal dog Samson, who is trained to stop her from self-harming, can be seen using his paws to keep Danielle from hitting herself.

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Officers on the scene after Miss Jacobs, whose video of her dog helping her during a meltdown attracted two million views, was killed by officers in her home in Mesa, Arizona

'Please no negative comments this really happened and it's not easy to open myself and share what it's like on a daily basis,' she added in the caption.

The video begins with Danielle, from Arizona, standing and crying as she pounds her chest with her fist. Samson immediately jumps up and uses his paws to pull her arms down.

Danielle continues to sob, and soon, she is repeatedly hitting her head with the palm of her hand. One again, Samson jumps on his two feet as he pushes her hands away.

When Danielle finally sinks to the ground, Samson curls up next to her and licks her face.

'This is what's considered a meltdown,' Danielle explained of the footage. 'Yes, Samson is alerting. I trained him to alert to depressive episodes [or] self harm [but] not both, but [still] he alerted.'

She added: 'It appears the response is late, but it's actually supposed to be as I'm coming out of the meltdown as I tend to have a panic attack after.'

It is one of a number of videos she has posted about her experiences with the condition, including one where she is devastated at not being given support in quest for a college education.

The video has recently been made private but had been viewed more than two million times since it was posted, with many people commending Danielle for sharing such a private moment.

Protective pet: Danielle Jacobs' dog Samson can be seen jumping and using his paws to stop her from hitting herself

Man's best friend: Samson can be seen pulling Danielle to the ground (L) where he continues to comfort her (R)

'As an older brother to a 13-year-old boy with autism, this is truly heart-warming and powerful. Thanks for sharing,' one person wrote.

The added: 'EDIT: I didn't realize that YOU are the one who uploaded this video! Very courageous of you to do so. You are very lucky to be so intelligent and highly-functional with ASD. Best of luck to you in life! [sic]'

Another poster whose son has autism agreed.

'It is very brave of you to share your most fragile moments with the world,' he wrote. 'My son has Autism and his meltdowns are also heartbreaking to watch. Many, many people who have heard about meltdowns but, have never actually seen one, will finally understand how traumatic they can be. Thank you! [sic]'

He added: 'Also, this is another example of how our pets are emotionally connected to us much more than we may realize. Your dog is awesome.'

And many other noted how wonderful it is that Danielle has Samson to turn to in times of need.