A 20-year-old man has been arrested over the brutal murder of young international student Aiia Maasarwe whose slain body was found near tram tracks in Melbourne.
Homicide detectives moved on the man at 11.20am in the northeastern city suburb of Greensborough, two days after the killing of Ms Maasarwe, 21, in nearby Bundoora.
"The arrest followings an extensive investigation into Aiia's death following the discovery of her body near Main Drive and Plenty Road in Bundoora on Wednesday 16 January about 7am," a Victoria Police statement read.
"Police would like to thank the public for their assistance with the investigation."
News.com.au has contacted Victoria Police for comment.
The development comes today as further details of the final hours of Ms Maasarwe's life emerge.
Final hours of Aiia's life
Earlier, police said while hunting for the woman's killer that the person responsible had left behind clues and that somebody saw him come home.
On Wednesday morning, the 21-year-old's body was found a short walk from a tram stop and not far from the safety of the campus where she lived.
The night prior, she attended a Melbourne walking tour between about 7:00pm and 8:00pm.
Event organiser Arun Chandran took a photo of the group, which shows Ms Maasarwe smiling, at 7.56pm, just hours before she was killed.
Chandran said Ms Maasarwe had joined a few of the "Let's Talk In English" group's tours in the past.
"She was very friendly, knowledgeable, easy-going, and someone who knew a lot. It was quite refreshing to talk to her," he said.
"Aiia was studying English at La Trobe University. She was such a positive and friendly person."
Ms Maasarwe then attended a comedy show in North Melbourne before heading home.
Detectives say it's likely Ms Maasarwe had been stalked on the route 86 tram from Docklands before she was attacked and killed at about 12.10am, less than a kilometre from her home.
The killer then discarded clothes, including a black hat and a black and grey T-shirt and dumped Ms Maasarwe's body in shrubs near a shopping centre. Her slain body was discovered by workers early on Wednesday morning.
Police say it's likely the victim's killer was covered in blood, and that somebody knows who he is.
Homicide Detective Inspector Andrew Stamper said the "absolutely horrific" and "random" attack was inflicted on a completely innocent member of the community.
"Nothing in the victim's background indicates this was anyone known to her," he said.
"So yes, unfortunately, the presumption at this stage is this was a random and opportunistic attack."
Earlier, former homicide squad detective Charlie Bezzina has warned the murderer could strike again if they are not caught soon.
"It's imperative that those who have knowledge of some sort … assist police," he told 3AW. "This person will be known to somebody.
"The potential is there for him to kill again. They've got to live with their conscience. If this person or persons strike again, they have to live with that and say could I have stopped that?"
It comes as the victim's family says police aren't doing enough.
In an interview with the ABC, one of the murdered teen's uncles expressed "disappointment" at authorities in Australia.
"We are very disappointed in the authorities," he said. "They bring us a cadaver. I cannot believe it."
A vigil is being planned for Ms Maasawre tonight. Mourners will gather on the steps of Melbourne's Parliament House to remember the young woman whose life was taken too soon and to protest against another senseless, violent attack on a woman walking home.
Organiser Jessamy Gleeson, who helped thousands of people gather for a vigil for murdered Melbourne woman Eurydice Dixon last year, said it was important Melburnians stood together.
"None of us would want to be doing this, to be organising something like this; it was just a point of creating a space and making visible the victims who are made invisible far too quickly," she told news.com.au.
"That's the point. It's a way of making things visible."
One way it's hoped to achieve that is by asking those in attendance to wear black and stand out against the backdrop of the parliament steps.
Gleeson said the vigil will last two hours, from 6pm to 8pm, and people are welcome to come and go as they please. There will be no speeches or music, just silent reflection.
Superintendent Tony Ryan said yesterday that police were doing everything possible to catch the killer.
"We've got an ongoing effort to saturate the area as much as we possibly can," he said.
"We've got uniform cars, we're supported by the operational response unit, we've got detectives, we've got our community police, we've got Transit working on the tram lines.
"As part of our security in the area we'll conduct an audit on it and see if we can get some immediate improvements."
One possibility police have not yet ruled out is that Ms Maasarwe's sister was speaking to her when she was attacked. Her uncle Rame Massarwe said the pair were on FaceTime when "her phone fell".
"She was talking to her sister and seemed OK, but then her phone fell and then she heard different voices," Mr Masarwe told the Herald Sun.
Victoria Police released CCTV images of Ms Maasarwe which shows the clothing she was wearing that night, in the hope someone saw her and can help police track her exact movements.
The T-shirt and cap found discarded at the scene are "suspicious", police say. The black hat has '1986' printed on it and the T-shirt has a grey body and black short sleeves.
Another of Ms Masarwe's uncles, Abed Katane, told Israeli news outlet Haaretz the family was in shock.
"She was an excellent student, full of life, and was in a country that was not dangerous at all, to say the least. And despite that, we get this incredibly painful news," he said.
"It's the kind of thing you never expect."
— with Ben Graham