Man Haron Monis, a 50-year-old Iranian-born, self-styled cleric with a lengthy criminal history, burst into a downtown Sydney cafe on Monday wielding a shotgun, taking 17 people inside hostage. The siege ended 16 hours later when police stormed into the cafe to free the captives, two of whom were killed in a barrage of gunfire, along with Monis.

"This has been a horrific wake-up call," Prime Minister Tony Abbott told Macquarie Radio. "This was an atrocity — it may well have been a preventable atrocity, and that's why this swift and thorough review is so important."

Abbott has ordered a sweeping government review of the siege and the events leading up to it, including why Monis was out on bail and how he obtained a shotgun despite the country's tough gun laws.

Court documents detail Monis' long history with the law. In 2011, Noleen Hayson Pal — his ex-partner and mother of their two sons — went to police after she said Monis threatened her life. He was subsequently charged with stalking and intimidation intending to cause fear of physical or mental harm.

Pal testified in January 2012 that Monis said to her, "If I don't get to see the boys more than I am seeing them now, I'll make sure you pay for it — even if it means I have to shoot you."

Pal said she feared he would carry through on his threat, noting that he'd once told her he had a gun license. She said he grew increasingly paranoid when "he started getting more into his Islamic activities," insisting on drawing the blinds and shutting all the doors when he visited her house. She also accused him of slapping their eldest son in the face.

"He's always saying to me that people are watching, people are hearing our conversations," she testified.

Monis was ultimately found not guilty of the charge. A year later, Pal was stabbed to death and set on fire.

Police charged Monis' then-partner, Amirah Droudis, with Pal's murder, and charged Monis as an accessory. Both were out on bail on the charges when Monis launched his siege on the cafe on Monday. He was also facing dozens of charges of sexual assault dating back to 2002, and had been granted bail on those charges as well.

Monis was convicted and sentenced last year to 300 hours of community service for sending what a judge called "grossly offensive" letters to families of soldiers killed in Afghanistan between 2007 and 2009.

Just three days before he began his siege, Australia's highest court refused to hear his appeal of the convictions for sending the letters. The next business day, Monis walked into the cafe, a short stroll from the courtroom where the ruling was delivered.

"Just like about everyone else from the premier down, I was incredulous and exasperated at this," Abbott said. "This guy has a long history of violence, a long history of mental instability, he has a long criminal record and obvious infatuation with extremism. It was extraordinary he was on our streets."

New South Wales Premier Mike Baird concurred, saying, "I'm as outraged as everyone else."

New South Wales Attorney General Brad Hazzard said he has asked the director of public prosecutions to review all cases where bail has been granted and where there are any similarities to Monis' case.

Federal Attorney General George Brandis said it appeared the type of gun Monis used during his siege was banned in Australia, though he said an investigation was needed to confirm that.

Katrina Dawson, a 38-year-old lawyer, and Tori Johnson, the cafe's 34-year-old manager, were killed during Monis' rampage. Officials have not said if they died in crossfire as police stormed in or were shot by their captor. Their autopsies were expected to be completed later Thursday.

At least three of the hostages remained in Sydney area hospitals Thursday, according to hospital spokeswomen.

Forty-three year-old Marcia Mikhael, a project manager at Westpac bank who suffered gunshot wounds to her leg during the siege, was in stable condition at the Royal North Shore Hospital. The hospital earlier discharged a police officer and a woman who suffered back pain during the siege.

A 52-year-old woman remained in stable condition at the Prince of Wales Hospital. And at least one hostage remained at the Royal Prince Alfred Hospital, although the hospital declined to provide further details.