YACQUB Khayre was a violent criminal, a terribly-behaved prisoner, and a one-time terror suspect with known links to extremists.

After serving time for a violent crime and having his parole eligibility date pushed back due to “poor behaviour” behind bars, the 29-year-old was released on parole last year, having to adhere to strict terms and conditions.

Still, on Monday night, he was able to lure a female escort to meet him at a bayside Melbourne hotel, shoot dead a man who worked at the serviced apartment block when he arrived, hold the woman hostage, then start a gunfight with counter-terror officers and shoot three before being gunned down.

As Prime Minister Malcolm Turnbull put it, there are “very, very grave questions” to be answered over why this dangerous man was able to carry out this attack, which police are treating as an act of terrorism, in the name of Islamic State and al-Qaeda.

Victorian Police commissioner Graham Ashton this morning confirmed the man behind the fatal Brighton siege had been on parole at the time of the incident.

“He is someone that was known to us as having a long criminal history, a whole range of offending going back many years ago.”

Khayre had come to the attention of New South Wales police and the Australian Federal Police back in 2009 when he was charged over a terror plot targeting Holsworthy barracks.

If not thwarted, the attack could have seen high numbers of Australian Defence personnel killed at the Sydney army base.

Khayre was acquitted of charges over that attack, but was known to have had links to the Somalia-based IS-linked terror group that the plot was traced back to.

Since walking from the Holsworthy trial in 2010, he had been convicted with “a whole range of offending”, and had spent about two years in a youth justice centre for between 42 and 45 offences, including multiple burglaries, assault and drug possession.

During his time in youth detention he was sentenced for stabbing a man on a train in the leg, demanding his money and phone.

According to AAP, court documents reveal Khayre came to Australia via a Kenyan refugee camp with his grandparents and had a “difficult” relationship with his parents who later followed.

Khayre lost his “steadying influence” after the death of his grandfather, a respected leader of the Somali community that was establishing itself in Melbourne.

He didn’t finish school, was “seriously” abusing drugs and alcohol and started committing offences, the documents show.

In sentencing Khayre for a 2012 aggravated burglary, Judge Felicity Hampel questioned whether he would be able to reform.

“It would appear that each time you have been released from detention or custody, you have rapidly turned back to drug abuse, and nothing has been put to me to indicate that you demonstrate any will or commitment to address it,” she said. “This unfortunately, is not your last matter before a court.”

Mr Ashton said the offender had most recently done prison time for “reckless intentionally causing injury while in prison, as well as for an arson while in the correctional system”.

Despite this series of offences while behind bars, Khayre ultimately qualified for parole, a decision Victorian Premier Daniel Andrews has defended.

“I would make the point that he had served significant jail time and become eligible for parole at a later point than he might have hoped because his sentence had been increased because of poor behaviour — this is the advice that I have — terrible behaviour in prison,” he said.

Still, Mr Andrews defended the offender’s parole, saying he “was eligible” and had “been compliant with the terms and conditions of the parole granted to him”.

“I would point to the fact that the sentence did not relate to terrorism acts. He was actually acquitted of (terrorism) charges in New South Wales, as we all know,” he said. “The jail sentence and his parole was in relation to other criminal acts that weren’t of a terrorism nature.

“Of course it is of concern to us that somebody who would be compliant with each and every term and condition of the parole they had been granted and were eligible for, could commit such a crime.”

Mr Turnbull said Khayre’s attack was a “shocking, cowardly crime”, made more so by the fact that he was “only recently released on parole”.

In response to questions around the man being able to spark the deadly siege while on parole, Mr Turnbull indicated the Premier had questions to answer over parole conditions in the state.

“There are some very, very grave questions. I have raised these today with the Victorian Premier,” Mr Turnbull said. “How was this man on parole? He had a long record of violence ... he had been charged with a terrorist offence some years ago and had been acquitted. He was known to have connections, at least in the past, with violent extremism, but he was a known, violent offender. How was he on parole?”

Mr Turnbull said there had been “too many cases of people on parole committing violent offences of this kind”.

He said the issue of parole would be a “high priority” at this Friday’s Commonwealth Heads of Government meeting.

The Prime Minister pointed to the case of murdered Melbourne woman Jill Meagher, whose killer Adrian Bayley was on parole when he raped and murdered the young ABC employee. He also pointed to the case of the Lindt cafe gunman Man Haron Monis, around whom similar questions were raised.

The Victorian government has a recent history of violent crimes executed by parolees.

“You mentioned Jill Meagher’s case, but there have been other cases as well,” Mr Turnbull said. “It is clear that this is a real issue where people with known records of violence, including people with known terrorist connections or at least connections with extremists have been released on parole. This is an issue that I will be raising and discussing with the premiers on Friday.”

Police have said there was “no indication” that Khayre was planning an imminent attack.

The parolee had complied with his parole conditions, including undertaking drug tests, attending appointments, and observing a curfew, the Premier assured.

On Monday however the hostage-taker tampered with the GPS ankle bracelet he was required to wear as part of his parole conditions while the siege was under way, Corrections Victoria has confirmed.

“He was known to us but there is nothing to suggest there was any indication yesterday was imminent,” Mr Ashton said. “Certainly we don’t know yet what caused him to go off like he has last night with undertaking the acts that he has.”

Investigators are currently seeking to determine the level of planning that went into the siege and the events that followed, and whether there were any others involved.

Mr Ashton said there was no indication at this stage that Khayre’s actions were planned in concert with others.

“We believe at this stage with the information we have he was acting alone and there wasn’t any sort of ongoing threat in relation to any plot or anything around this individual,” he said.

Do you know more? Email elizabeth.burke@news.com.au