A man accused of stabbing three people, killing one, had fled intensive in-patient mental health treatment while being transferred between hospitals.

The disturbing detail, revealed by the Nine Network on Tuesday, comes just hours after the man was arrested in the backyard of a property on Smythe St in Merrylands, in Sydney’s west, after the stabbing spree at about 10am.

Two people were raced to Westmead Hospital in a critical condition, including a 22-year-old man with neck injuries and a woman, 47, with wounds to her abdomen and chest. 

Another man, aged between 30 and 40, died at the scene.

Security footage filmed on Railway Terrace showed the alleged killer dressed in a white shirt and hat, and walking with his hands on his hips – as though he was out of breath.

He could then be seen running past a woman pushing a pram.

Police claimed the man stabbed multiple people with what was believed to be a kitchen knife up to 30cm long, before he fled the scene.

The man was arrested and taken to Granville Police Station.

A man accused of stabbing three people, killing one, had fled a mental health facility days earlier (pictured is the accused stabber running near a woman with a pram)

The man was arrested after three people were stabbed in Merrylands, west Sydney, at about 10am on Tuesday

A suspect has been detained by police but has not yet been charged 

It’s understood the man absconded from his treatment 10 days before the allegedly attack.

He was previously known to police for petty crime and mental health episodes.

Western Sydney Local Health District confirmed a patient undergoing acute mental health treatment for a complex condition was ‘alleged to be involved in the incident’ on Tuesday.

‘This person absconded from care while being transferred from Cumberland Hospital to Westmead Hospital emergency department for further medical assessment,’ it said.

‘NSW Police were notified, and contact was made with the patient’s family, but all attempts by [Western Sydney Local Health District] to contact the person were unsuccessful.’

A formal review into the man’s treatment, including examination from an external senior psychiatrist, will be complete.

‘We also extend our sympathies to the first responders who have been impacted by this incident,’ Western Sydney Local Health District said.

A crime scene was established spanning 50 metres along Merrylands Road, where the alleged victims were attacked.

The man was arrested in the backyard of a property on Smythe St in Merrylands (above)

One man, aged between 30 and 40, died at the scene of the stabbing

Guildford resident Joseph Ruissi told the Daily Telegraph he saw a man tending to the female victim’s neck in the aftermath of the attack.

‘Blood was pouring down the side of her neck and across her chest and she was coughing blood from her mouth,’ he said.

He said the shopkeeper was trying to staunch the bleeding, adding: ‘She started to slump to the side and you could tell she was dying.

‘Every second felt like a year. It was absolutely terrible. I just pray to God that whoever survived is going to get better.’

Superintendent Simon Glasser said the incident was ‘highly confronting’. 

‘It’s a horrible offence to have taken place in Merrylands just prior to lunchtime with lots of people around,’ he told reporters.

He said there was no relationship between the three victims, who were by themselves on Merrylands Road when the stabbing occurred. 

‘The alleged offender is known to police for petty crime and a number of mental health incidents,’ Superintendent Glasser said.

Police believe the attack was carried out with a kitchen knife up to 30cm long

Detectives seized a knife from a garden in the suburb which has been taken for testing 

The accused stabber was arrested and taken to Granville Police Station

‘He is not linked to the address he was located. 

‘However, he is a local to the area.’

Supt Glasser said ‘most of his history with us is mental health-related’. 

Once charges are laid, the alleged killer will face court.