The Australian government failed to heed numerous warning signs over many years that Man Haron Monis, the self-described Muslim cleric killed along with two hostages Monday at the end of his siege of a Sydney café, was a dangerous, unstable extremist capable of violence. One of the most pressing questions in the wake of the 16-hour hostage crisis is how a man who had recently publicly declared allegiance to the Islamic State terrorist group, had been charged with being an accessory to his wife’s murder, sex offenses and other crimes, and spoke with open disdain of the West, was allowed to live a free life in Australia.

Monis, an Iranian national, was not on any terrorist watch list, according to Australian Prime Minister Tony Abbott, who echoed the question many around the world are asking in remarks to reporters just hours after the siege ended. “If I can be candid with you, that is the question we were asking ourselves around the national security committee of the cabinet today,’’ Abbott said, according to The Australian. “How can someone who has had such a long and checkered history not be on the appropriate watch lists and how can someone like that be entirely at large in the community? These are questions we need to look at carefully, calmly and methodically.’’

Both the Australian and Iranian governments were long aware that Monis was believed to be a dangerous man with a violent history of mental instability who had latched on to militant Islamic rhetoric. But Monis was still able to walk unhindered into the Lindt Chocolat Café in central Sydney and initiate a deadly showdown with police that gripped the world and served as a stark reminder of the real dangers posed by lone-wolf Islamic terrorism.

Red flags about Monis, whose given name is Mohammad-Hassan Manteghi, were plentiful and came in many forms and from multiple sources, over a period of years. As recently as last month, Monis, who described himself as a Shia Muslim cleric, claimed that he converted to Sunni Islam in a statement he posted on his website earlier this month. He went on to pledge allegiance to the Sunni-aligned Islamic State terror group, also known as ISIS or ISIL, and posted a photograph of himself wearing a garment on his head affiliated with the organization.

Haron was born in Borujerdi, Iran, in 1964. He claimed in a 2001 interview with Australia’s ABC Radio National that he was “involved” with Iran’s intelligence services before he ran afoul of the nation’s government and fled to Australia, where he was granted political asylum in 1996. As of the 2001 interview, Monis described himself as a Shia Muslim Ayatollah and spoke effusively about the West, saying that while he believed the Iranian regime is against human rights, Australia had deep respect for religion.

“I don't want to say it is perfect, we don't have a perfect society on the earth, but when we compare, if we compare Australia with Iran and other countries in the Middle East, we can say it is heaven,” he told ABC Radio at the time. But sometime between then and this week, Monis seemingly morphed into a different person, adopting a radical Sunni ideology, aligning himself with ISIS and making the decision to execute a brazen terror attack in the heart of Australia’s largest city.

Monis’ path to that day was anything but conventional, as he was for years seen as a fraud, and over the past two decades he earned an impressive rap sheet that spanned both Australia and Iran. In January 2008, Australia's senior Shia leader, Sheik Kamal Mousselmani, told The Australian that no Shia leaders in the nation “know him and we have got nothing to do with him.” He went on to urge the Australian police to “investigate who he is. It should be their responsibility.”

Iranian authorities informed their counterparts sometime around 2000 about a $200,000 fraud Monis allegedly committed in connection with an Iran-based tourism agency where he served as managing director in 1995. “It lasted four years to collect evidence on Manteqi’s identification documents and we reported this to the Australian police, but since Australia has no extradition treaty with Iran, they didn’t extradite him to Iran,” Iran’s Chief of Police Brig. Gen. Esmail Ahmadi Moqadam said Monday, adding that Monis left Iran in 1996 to avoid scrutiny in connection with the alleged fraud, the Tehran-based Mehr News Agency reported.

Iranian authorities repeatedly warned its Australian counterparts about Monis’ “psychological conditions,” mental instability and criminal history, but their concerns were always rebuffed, and the Australian government refused to send Monis to Iran to face the charges against him, Foreign Ministry spokeswoman Marzieh Afkham told Iran’s state-run Islamic Republic News Agency this week.

Monis was also charged as an accessory to the murder of his ex-wife, Noleen Hayson Pal, who was stabbed and set on fire on April 21, 2013, in a suburban Sydney apartment building. He was granted $10,000 conditional bail by the presiding magistrate, who said the prosecution had a “weak case” against him and the woman charged with killing Pal, Monis’ then-girlfriend, Amirah Droudis, Australia’s The Age reported.

But prosecutors allege that he went to great lengths to establish an alibi for the time of Pal’s murder, from pretending to suffer a heart attack, getting in a car accident, faking a robbery and more, according to The Australian, which reported that Monis and Pal were in the midst of a custody battle at the time of her death.

Monis went on to be charged with more than 40 sexual offenses in April, while he was out on bail in connection with his ex-wife’s murder. He allegedly sexually assaulted a series of women while posing as a “spiritual healer” over a period of years, according to Sky News. He was given bail on those charges as well.

Monis -- who called himself Sheik Haron -- also raised controversy by sending letters insulting Australian troops to their families, comparing them to murderers and saying they would go to hell. Monis was sentenced to 300 hours of community service and put on a two-year “good behavior bond,” a sentence similar to what Americans call probation, Australian Associated Press reported.

The full story of how Monis came to besiege Sydney will likely take some time for investigators to compile, but in the meantime the Abbott government is embarking on some soul-searching to answer that most important question: How could this happen?