In November 2019, Michael Paul Forrest, wearing a face covering, exited a Hyundai Getz while holding a long-barrelled rifle and approached the woman sitting in her parked car at the intersection of Dominion Circuit and New South Wales Crescent.

Court documents state that he initially tapped the window with the gun before shooting through it and injuring her.

While still in shock, she was able to start the car and drove away - when she saw the Getz appearing to follow her - towards Manuka Oval before calling triple zero.

She was taken to Canberra Hospital where she was found with a bullet lodged in her neck. It also struck a tooth.

Police arrested Forrest later that morning when they found him slumped over the steering wheel of the Getz.

Forrest, 28, fronted the ACT Supreme Court on Monday after pleading guilty to attempted aggravated robbery, assault occasioning actual bodily harm and unauthorised possession of a firearm.

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He sat still as the victim's impact statement was read to the court.

"My life irrevocably changed forever. My husband almost lost his wife, my children almost lost their mother, my parents their daughter," the court heard.

"The person I was when I left home at 7.48am is no more ... that person was lost forever just 32 minutes later."

The victim said said she needed to draw him away from the school area.

"Imagine if they had stayed in that area ... it causes pause," she said.

She describes Forrest's offending as heinous and as "terrorising that day".

"He has stolen my confidence. He has stolen my trust, he has stolen my way of life," she writes.

"After knowing what my injuries actually were, I'm glad I was able to find help as quickly as I did at Manuka Oval.

"I knew I was bleeding, but I thought it was only from the glass. I didn't know there was a bullet lodged in my neck."

The victim wrote that she had surgery to remove the bullet and glass fragments that have caused lifelong damage.

"His act is unforgivable. I am mentally and physically scarred for life," she said.

Crown prosecutor Katie McCann argued for a harsher sentence compared with previous ones after Forrest was "given the benefit of a fairly low non-parole" in 2017.

Ms McCann said while it was clear that Forrest began an illicit substance addiction as a child, any mitigating effect of the need for rehabilitation for that addiction would "assume less significance" because he had not taken previous chances to improve his life.

"Some five days after being granted parole, he began to take drugs and then engage in what can only be described as a criminal rampage that followed," she said.

Ms McCann said other sentencing purposes - especially community protection and deterring Forrest - must take priority and that he committed the latest offending while on conditional liberty.

"Any expression of positive attitude towards rehab must be approached with some degree of scepticism," she said.

Defence lawyer Sam McLaughlin conceded that the assault was a serious example of its type, but that the objective seriousness of the carjacking was low compared with other cases as it did not have planning or premeditation.

"The robbery here is spontaneous, unsophisticated and relatively short lived," he said.

Mr McLaughlin argued for leniency based on the interplay among his client's illicit substance abuse, childhood trauma and mental health issues.

The defence lawyer said Forrest is set to start trauma counselling for the first time and that he was at risk of being further institutionalised in jail.

Chief Justice Helen Murrell will on Tuesday sentence Forrest for the carjacking incident and a host of other offending in late 2019 and April 2020.

These include trying to arrange a drug delivery into the Alexander Maconochie Centre, as well as other aggravated robberies, property damage, burglary, and driving offences.

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