Accused Sydney stabber Mert Ney filmed taking selfie after alleged crime

The man accused of stabbing multiple people in Sydney's CBD on Tuesday appears to have taken a selfie just minutes after committing one of his alleged crimes.

Mert Ney was captured on CCTV footage walking through a back alley on Clarence St, after leaving an apartment where he is alleged to have killed 24-year-old Michaela Dunn

The video shows him stop and look at his phone, before appearing to take a selfie.

The 20-year-old is accused of slitting Dunn's throat before going on to stab another woman, who survived, at a nearby hotel.

Footage filmed by onlookers after the alleged stabbings shows Ney walking down York St brandishing a large knife. He was eventually captured by members of the public who used chairs and a milk crate to restrain him before police arrived.

According to 7News, police believe he had visited the apartment on Clarence St "for the purposes of prosititution", and had phone contact with Dunn before his arrival. 

Police said Ney had a history of mental illness and had recently checked himself in to a mental health facility. A week before the alleged stabbings, he was seen in Blacktown Hospital looking distressed, according to 7News, which obtained video footage from the hospital. Ney's sister said his mental health had recently deteriorated. 

"I just wanna say sorry to the family. Sorry a million times, sorry for everything," she told reporters.

Information found on Ney suggested he held some "ideologies related to terrorism", police said in a statement after the deaths, but he "has no apparent links to other terrorist organisations". He was, "by definition a lone actor".