SYDNEY

- Australia's prime minister acknowledged earlier today that the nation's security system failed to keep track of a gunman responsible for a deadly siege at a Sydney cafe, and promised a transparent investigation into why the man was not on any terror watch list despite having a long criminal history.

Man Haron Monis, a 50-year-old Iranian-born, self-styled cleric described by Prime Minister Tony Abbott as deeply disturbed, took 17 people hostage inside a downtown Sydney cafe on Monday. Sixteen hours later, the siege ended in a barrage of gunfire when police rushed in to free the captives. Two hostages were killed along with Monis.

"The system did not adequately deal with this individual," Abbott conceded today. "Two very decent people are dead, others are injured, others are traumatized because of a madman who was roaming our streets."

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 from 2007 to 2009. He later was charged with being an accessory to the murder of his ex-wife. Earlier this year, he was charged with the 2002 sexual assault of a woman. He had been out on bail on all the charges.

Just three days before Monis began his deadly rampage, Australia's highest court refused to hear his appeal against his convictions for sending the letters.

High Court documents show that Chief Justice Robert French and Justice Chief Stephen Gageler ruled at 9:50 a.m. on Friday that the full bench of their court would not hear Monis's constitutional challenge to his convictions. At 9:44 a.m. the next business day, a shotgun-wielding Monis walked into the cafe, just a short stroll from the courtroom where the ruling was delivered.

Abbott said the government would publish a report on how the siege unfolded, why Monis was not on the nation's terrorism watch list, and how he managed to obtain a shotgun in a country with strict gun ownership laws.

Thousands of tearful Australians continued to pour into Martin Place today, a plaza in the heart of Sydney's financial and shopping district where the Lindt Chocolat Cafe - the site of the siege - is located. A makeshift memorial had grown into a mountain of flowers left to honor the hostages killed: Katrina Dawson, a 38-year-old lawyer and mother of three, and Tori Johnson, 34 and the cafe's manager. Officials have not said how the two died.