The self-styled sheikh behind a siege at a Sydney cafe had been charged as an accessory to murder and with multiple sexual offences. He also harboured deep grievances against the Australian government and had found little kinship in the city’s large Muslim community, where he was seen as deeply troubled.

Man Haron Monis, an Iranian refugee described by those who knew him as a loner, was killed early yesterday after heavily armed police stormed the Lindt Chocolate Cafe to end a 16-hour hostage drama that made global headlines.

Last year Monis was charged as an accessory to the stabbing murder of his ex-wife, who was set alight in a Sydney apartment block. He was charged this year with more than 40 counts of sexual or indecent assault against women in Sydney, according to court documents.

He was also found guilty in 2012 of sending threatening letters to the families of eight Australian soldiers killed in Afghanistan and sentenced to two years in prison, although he served only a portion of that penalty. Those charges and the conviction, as well as public statements Monis made on his website, have raised questions in Australian media about whether authorities should have done more to monitor him.

He was a very, very, very unusual guy, and he had no affiliations with any group

Prime Minister Tony Abbott told reporters that Monis was well known to police. When asked by a journalist whether it was appropriate for Monis to have been granted bail for the murder charge, New South Wales state Premier Mike Baird declined to comment.

Monis’s website, now taken down by authorities, painted a picture of a man unravelling, enraged by Australian courts and by perceived injustices against Muslims in Iraq and Afghanistan.

“Man Haron Monis ... has continuously been under attack and false accusation by the Australian government and media since he started his political letter campaign from 2007,” Monis wrote on the website.

He also railed against what he said was a decision by a court to prevent him from seeing his children.

Sydney-based criminal defence lawyer Adam Houda, who represented Monis over the letters sent to the soldiers’ families, described him as a deeply unsettled loner, wholly apart from Sydney’s tight-knit Muslim community.

“He was a very, very, very unusual guy, and he had no affiliations with any group. He operated alone. He was a lone wolf,” Houda said.

A source close to Sydney-based Islamists said Monis did not belong to any local radical group and that leading figures held him in contempt.

In December Monis seemed to suggest on his website that he had switched from Shi’ite to Sunni Islam, which would help explain media reports that he had demanded police bring a flag from militant Sunni Islamist group Islamic State to the cafe.