Monis was described by Abbott as having indicated a "political motivation,"[9][10] but the eventual assessment was that the gunman was "a very unusual case—a rare mix of extremism, mental health problems and plain criminality.

It has been reported that the Australian Security Intelligence Organisation followed up on the call by reviewing the website and Monis's posts on social media but found nothing to indicate that he was likely to commit an act of violence.

This was relayed by hostage Marcia Mikhael, who said that she "lost it" when told that the Prime Minister was too busy, saying, "I don't care what [Abbott] is doing right now...I'm sure there's nothing more important happening in Australia...than the lives of the people in this café..."[36] Mamdouh Habib said he knew Monis well and offered to help the NSWPF negotiate with him.

[4][15][28] At around 4:58 pm, two female hostages, both employees, Jieun Bae and Elly Chen, escaped by running from another entrance of the building and were met by Tactical Operations Unit officers.

[89] The other hostages were identified as John O'Brien, Stefan Balafoutis, Elly Chen, Jieun Bae, Harriette Denny, Viswakanth Ankireddy, Joel Herat, Fiona Ma, Jarrod Hoffman, Puspendu Ghosh, Selina Win Pe, and Julie Taylor.

[15] Police advised people in the area bounded by Hunter, George, Elizabeth, and Macquarie streets, bordering Martin Place, to remain indoors and away from windows.

[111] Monis had been charged with accessory to murder relating to the death of his former wife who was found stabbed eighteen times, and set alight, on 21 April 2013 at a unit block in Werrington.

[7] Jeremy Gormly SC, counsel assisting the inquest, summarised Monis as "a complex, disturbed individual desperate for recognition and status but completely lacking the skills or achievements to bring that dream to life".

[19][127] The Lord Mayor of Sydney, Clover Moore, on the morning of 16 December, urged Australians to see this as a "one-off event", stating, "We're an inclusive multicultural community and we need to deal with this together".

[128] Governor-General of Australia, Sir Peter Cosgrove, released a statement sympathising with the families, commending the work of the police involved, and urging Australians to "unite in our resolve to protect what we value most—our way of life, our care and respect for each other".

Johnson's father was accompanied by rabbis Levi Wolff and Zalmen Kastel, Hindu priest Pandit Ramachandra, the Reverend Bill Crews and Sheikh Wesam Charkawi.

This sought to offer solidarity and emotional support to Muslims travelling alone on public transport by people tweeting their bus/train route and suggesting that they would be willing to "ride with" anyone who might feel threatened.

[152] The Catholic Archbishop of Sydney, Anthony Fisher, invoked the special prayers in the Roman Missal from the "Mass in times of civil disturbance"[153] and a memorial service was held at St Mary's Cathedral, on the morning of 19 December.

"[155] Iranian Foreign Ministry spokeswoman, Marzieh Afkham, strongly condemned the taking of hostages as "inhuman" and also stated that the Australian authorities had been repeatedly warned about Monis.

[169] Two weeks after the siege, Dabiq, a magazine published by the ISIL editorialised on Monis's actions and attempted to claim him as one of their own, in a response that an expert described as "absolutely predictable".

It suggested only modest changes to laws and procedures, taking the view that "introducing substantial further controls involves a larger choice about the sort of society we wish to live in and is properly the province of the public and our elected representatives".

"[192] The Australian prime minister said, "[Man Haron Monis] had a long history of violent crime, infatuation with extremism and mental instability...As the siege unfolded yesterday, he sought to cloak his actions with the symbolism of the ISIL death cult.

"[193] Prof Greg Barton (from Deakin University) and Dr Clarke Jones (ANU) told the inquest that Monis was a loner and had mental health problems, and was desperate to attach himself to something.

"[192] Conversely, Yassir Morsi, a researcher at the Centre for Muslim and non-Muslim Understanding in Australia, suggested that "before he flew the black flag, Monis was just a desperate man with a violent past" and that "he was just another gunman.

According to psychologists and psychiatrists who study radicalisation, jihad propaganda and calls to kill infidels can push mentally-ill individuals to act, even in the absence of direct or personal contact with radical Islamists.

[204] In February 2017, United States President Donald Trump cited the Sydney siege as an example of what he claimed was deliberate underreporting of terrorist attacks by the media, notwithstanding that the event received "blanket coverage" in local and international news.

"[206] During the siege, an Australian Army Tactical Assault Group East team at Holsworthy Barracks evaluated the floorplan of the cafe and gave advice to police.

[68] During the siege, no significant effort was made to negotiate with Monis, as would normally be expected in a hostage situation in order to build a relationship with a gunman and persuade them to surrender.

[37] It has been suggested that the police treatment of the siege as a terrorist attack may have led to errors such as making no attempt to negotiate with the gunman as would have been normal practice in other hostage situations.

[215] In the absence of hard evidence, suggestions that Monis represented a growing trend of systemic failure, rather than being an aberration, were noted as dangerous to public confidence; to the separation of powers; to the idea of innocence till proven guilty and also to social cohesion by inviting suspicion of people from the Middle East.

[216] In the week after the siege, it was revealed that John Robertson, NSW Opposition leader, had sent a letter which passed on a request made by Monis, a constituent in his Blacktown electorate, to the Department of Family and Community Services in 2011.

The letter was, according to Robertson, routine procedure on behalf of a constituent and written in support of Monis's request for a supervised visit with his children on Father's Day despite an apprehended violence order against him.

[235] The premiere of Jonathon Welch's choral piece Street Requiem in February 2015 was dedicated to the siege victims and to those who died in the Charlie Hebdo shooting in Paris.

[237][238] Chan's Love Is Always Born (December), with original words by Michael Leunig and 'Silent Night' in Arabic, was commissioned and premiered by the Song Company at concerts around the first anniversary of the events.

Senator Dean Smith, a homosexual Liberal Party member, changed his views on same-sex marriage in Australia due to Tori Johnson and his partner of 14 years.