Caitlin O'Brien, 31, was murdered at her Melbourne home on June 25, 2019

Her boyfriend Shea Sturt, 32, pleaded guilty to murder at court on Friday

Court proceedings reveal a tragic history of sexual and physical violence

Doctors notes and police reports show authorities were aware of the abuse

As early as 2010, Ms O'Brien lodged a police report after having to flee her Chelsea home where she had been attacked by boyfriend Shea Dylan Sturt (pictured)

A murderer posted a series of cryptic messages on Facebook on the day he killed his girlfriend by stabbing her in the chest with scissors.

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Caitlin O'Brien, 31, was found dead inside the Melbourne apartment she shared with her boyfriend Shea Dylan Sturt, 32, on June 25, 2019, after police kicked down the door to conduct a welfare check.

The nurse had been stabbed in the chest a pair of scissors and smothered with a pillow.

After the brutal slaying Sturt approached police at Flinders Street train station and confessed to the murder, urging them to arrest him.

In the hours before her death he had shared a series of bizarre messages on his Facebook page, revealing he was losing his grasp on reality.

The posts included messages like 'you can't rape humanity away,' 'Sacrifice is beautiful but only ever for the right reasons,' and 'I forgive you'.

Ms O'Brien, 31, (pictured) was found dead on June 25, 2019 in her apartment at Gardenvale, in southeast Melbourne

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He also posted a video of a stand-up routine by Owen Benjamin called 'How To Be Married and Not Be Murdered'.

The mental instability was something O'Brien raised alarm about in a message exchange with her friend the day before she was killed.

'Shea's out of his mind. Having delusions he is Jesus. I'm just scared to be around him. He's not making sense at all. He forced me to eat an apple today so I could be like Adam and Eve and be enlightened,' she wrote.

Days earlier Sturt was released from the Alfred Hospital after a mental heath assessment.

In a message exchange between the two Ms O'Brien specifically told Sturt she was scared he would murder her.

In the hours before her death Shea Dylan Sturt shared a series of bizarre messages on his Facebook page, revealing he was losing his grasp on reality

That same day of Caitlin O'Brien's murder her boyfriend posted a series of cryptic messages (pictured) on Facebook, including 'You made me kill 'the devil' because you saw her in yourself'

Sturt pleaded guilty to murder at Melbourne Magistrate's Court on Friday.

While her killer is now facing years behind bars, the tragic circumstances leading up to Ms O'Brien's death paint a picture of broken support system for victims of domestic violence.

Shea Dylan Sturt (pictured) pleaded guilty to murder at Melbourne Magistrate's Court on Friday

Court proceedings reveal the young nurse endured years of abuse and sexual violence at the hands of her partner before the loss of her life on June 25.

The two began dating ten years ago after meeting as teenagers at TAFE, before an escalating history of family violence.

As early as 2010, Ms O'Brien lodged a police report after having to flee her Chelsea home where she had been attacked by Sturt.

He was charged with assault but placed on an adjourned good behaviour bond in September 2011.

In the two years before she was murdered, O'Brien visited her local GP 33 times and a series of damning notes from doctors between March 2017 to October, 22, 2018 revealed a knowledge she was being physically and sexually abused.

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One particularly explosive note included the message Sturt had 'attacked Caitlin saying he needs to kill her first before himself,' reports the Herald Sun.

Caitlin O'Brien, 31, messaged a friend on June 24, 2019 saying her boyfriend Shea Dylan Sturt, 32, was having delusions he was Jesus and she was scared to be around him

'Caitlin was a quiet but cheery girl who was extremely passionate about caring for others, which showed in the way she cared for her patients and their families,' a friend said

Another note revealed authorities were aware of Sturt's unstable mental health.

'Has been in a DV (domestic violence) relationship – fiance' was arrested – has history of psychosis,' a doctor's note read.

On June 25 2019, Sturt entered the Kooyong road flat where Ms O'Brien was recovering from brain surgery and fatally stabbed her in the chest with a pair of scissors.

Sturt then pushed her onto the bed, and held a pillow over her face to suffocate her before strangling her with a pair of tracksuit pants.

The case will return to the Supreme court on March 16 for a directions hearing.