An aspiring rapper arrested in relation to the death of Arab-Israeli student Aiia Maasarwe in Australia posted on Facebook a week before the incident "International girl Of mystery You knows who you are."

Codey Herrmann, a self-described rapper who went by the name MC Codez, was arrested by police at a park in Greensborough on Friday, two days after the body of Maasarwe was found near a shopping centre in Melbourne.

Herrmann, 21, attended Bundoora Secondary College until 2016. He went by several different names including Kody Wrex and Codey Kulla Kulla.

FACEBOOK Codey Herrmann, who went by the rapper name MC Codez, has been arrested by police in Melbourne.

In the hours after Maasarwe's body was found, he posted a photo of himself holding a can of Jack Daniels and a photo of himself as a baby, with the caption: "b4 An afta".

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A 21-year-old friend said she saw him around Bundoora a lot. He was believed to have been couch-surfing.

INSTAGRAM Israeli student Aiia Maasarwe was killed metres from a tram stop in Bundoora, in Melbourne's north.

"He was on the 86 tram a lot. He was always on foot, I never saw him transport in any other way. Trams and buses," she said.

Herrmann was being questioned by police on Friday night and had not been charged with any offence.

Other friends of Herrmann said he was a troubled teenager.

FACEBOOK Herrmann, 20, in a recent Facebook post.

Another former schoolmate said she saw him a week ago in Grimshaw Street, Bundoora less than 3 kilometres from where Maasarwe was killed. He appeared disorientated and was walking into oncoming traffic.

"When I saw him near Grimshaw Street he looked like he didn't care for his life," he said.

"[He] was walking in front of moving cars [and] crossing the street without looking."

PAUL JEFFERS/THE AGE Forensics police outside the Grimshaw Street property in Bundoora on Friday.

The friend who saw him often on the 86 tram said she had gone through primary school and high school with Herrmann, and they had been neighbours for many years. She said he and his sister were in foster care with a woman in Bundoora.

"Growing up he was a foster kid. He was a good kid growing up. As high school started he became a little bit depressed, a bit troubled and a bit into the drugs," she said.

"Most of his depression was because of his family stuff, he didn't have much family around at all. Just his sister, they were very close.

THE AGE Police have released CCTV of Aiia Maasarwe before she died.

"I know he has gone missing a few times and he had trouble with family stuff. He hung around Greensborough skate park and had a lot of friends in Greensborough."

It's understood he had family in Cape York in Queensland.

Tim Kefa, another schoolmate, said Mr Hermann had seemed like a normal student in his junior years but spiralled in his later years, battling with drug and alcohol abuse issues. "Everybody I have spoken to is in shock," he said.

AAP Police have released images of clothing believed to be worn by the killer.

Others recalled him being quiet and withdrawn.

In recent weeks, Herrmann posted photos of Southern Cross Station as he boarded a train to Bairnsdale, as well as discussing his mental health struggles and having "battled with the devil".

A post on January 10 read: "Shoutout to all the men going through a lot, with no one to turn to, because this world wrongly taught our males to mask their emotion & that strong means silent."

THE AGE A black cap and a T-shirt were found within 100 metres of the scene.

Herrmann was arrested in Greensborough about 11.20am on Friday. At the same time, homicide detectives and forensics police descended on a derelict, weatherboard house on Grimshaw Street, Bundoora.

It is understood he was identified as a key person of interest after forensic tests were conducted on clothing dumped not far from the scene.

Maasarwe was on her way home from a gig at The Comics Lounge in North Melbourne and was speaking to her sister on the phone via FaceTime when she was attacked.

On Tuesday night, she was with new friends at Flagstaff Gardens in the CBD to practise her English, before going to The Comics Lounge then taking the 86 tram back to Bundoora.