Police surround Sydney cafe
Police surround Sydney cafeReuters

Australian Prime Minister Tony Abbott said on Monday night (Tuesday morning local time) that the self-proclaimed Islamic “sheikh” who took more than a dozen people hostage in a cafe in Sydney had a history of “mental instability”, reports ABC News.

The man, identified by Australian media as Man Haron Monis, was killed by police during a rescue operation around 2:00 a.m. local time after a 16-hour standoff. Two hostages were also killed, authorities said.

Addressing the nation following the kidnapping, Abbott said that there is “understandably a lot of speculation” about exactly what happened and what prompted the incident, but he said Monis was “well known” to authorities.

Monis previously made headlines for sending hate mail to the families of fallen Australian soldiers, calling the dead murderers and child killers.

“He had a long history of violent crime, infatuation with extremism and mental instability,” Abbott said, according to ABC News. “As the siege unfolded yesterday, he sought to cloak his actions with the symbolism of the [ISIS] death cult.”

Earlier in the ordeal, hostages were made to hold up a black flag with Islamic text on it, similar to one associated with the Islamic State (ISIS), the terror group responsible for countless acts of brutality in the Middle East.

In videos purportedly made inside the cafe during the standoff, hostages relayed Monis’ demands, which included a proper ISIS flag and having politicians declare the incident an ISIS attack.

Monis was born in Iran as Manteghi Bourjerdi and migrated to Australia in 1996, according to Australia’s 9News.

A website that appears to have been made by Monis or his supporters says these latest allegations are “in fact political cases against this Muslim activist, not real criminal cases.”

Australia, which is backing the United States and its escalating action against ISIS, is on high alert for attacks by radicalized Muslims or by home-grown fighters returning from fighting in the Middle East.

ISIS terrorism has recently been on the rise in Australia, with police arresting 15 terror suspects who were members of an ISIS cell that was planning to behead a random member of the public in a campaign of terror.