Breaking: A man has been arrested in Sunshine in relation to the killing of Doncaster schoolgirl Masa Vukotic.

Police earlier revelaed that the suspect in the case stopped to ask a man for directions near the crime scene.

Masa was stabbed to death in a "random", daylight attack in a small park, less than a kilometre from her Doncaster home, in Melbourne's east on Tuesday evening.

Police released images taken from CCTV footage of a man boarding a bus on Doncaster Road in Doncaster at 7.09pm, about 20 minutes after Masa was killed in Koonung Creek Linear Reserve.

The man pictured in the CCTV image, whom police wish to speak to, was wearing a red T-shirt, black pants, sneakers and holding a white, plastic shopping bag. He also appeared to be carrying a black jacket under his arm.

Homicide squad detective Inspector Mick Hughes told ABC radio on Thursday that the man was seen by about four or five people running along on Heyington Avenue, near the footbridge where Masa was killed.

Inspector Hughes said the man stopped to ask another man on Heyington Avenue for directions to Doncaster Shopping Centre.

The witness has told police the man appeared nervous, but seemed to be familiar with the area.

"The person that spoke to him in Heyington Street, he says he appeared nervous and he got the impression when he asked him for  the directions to the Doncaster Shopping Centre he already knew the answer to the question," Inspector Hughes said.

"It was almost like he was trying to, I guess, lessen his suspicion."

It is believed the man travelled about 15 kilometres, before stepping off the bus at the corner of Hoddle and Johnston streets in Abbotsford.

Myki records sought

Inspector Mick Hughes said police were working to retrieve myki records of passengers on board the bus.

"That's a work in progress," he told radio station 3AW.

Inspector Hughes said detectives hoped to speak to the bus driver and passengers, particularly those who may have disembarked on Hoddle Street, to determine in which direction the man they wish to speak to walked off.

"We haven't had a chance to speak to the bus driver, or any passengers," he said.

It is understood detectives have approached Public Transport Victoria to access passengers' myki records.

Inspector Hughes said detectives were also working to find new CCTV footage of the last known location of the man pictured boarding the bus.

"My guys got about four hours sleep the night before last. They were back out there last night," he said.

"We'll be out there first thing this morning.

"We're back to square one this morning just going through information as it comes in."

Inspector Hughes said he was confident the man in the CCTV images would be recognised by people who knew him.

The scene

Masa was found with stab wounds in a small patch of bushland at the base of a footbridge near the corner of Heyington Avenue and Stanton Street.

A resident called triple-0 after hearing screams and seeing a person fleeing the Koonung Creek reserve on Tuesday evening.

The footbridge is used as a main thoroughfare for runners and cyclists over the Eastern Freeway.

The teenager was wearing headphones at the time and may not have heard her attacker approaching, Inspector Hughes said.

The daylight attack occurred in an area frequented by runners and cyclists only metres from houses, but Inspector Hughes said on Thursday that it was not safe for women to be alone in parks.

"I'm sorry to say that that is the case," he said.

He said police were first to arrive at the scene. Paramedics arrived minutes later to find the girl under cardiac arrest, but could not save her.

Masa's father, Slavoljub, and sister, Nadja, went to the scene shortly after she was found. Mr Vukotic's cries of grief were heard throughout the street.

A school's grief

The principal of Canterbury Girls' Secondary College has spoken of the "popular and respected" student whose violent death has shocked them all.

"Our school community is shocked and devastated by this tragedy," Principal Dr Mary Cannon said in a statement on Thursday.

"Masa was a very popular and respected student who had close friendships with many students.

"Our thoughts and wishes are with Masa's family at this incredibly difficult time."

Students and staff have had access to additional specialist counselling since Wednesday, she said.

"We are working to support the  family and will find an appropriate way to remember Masa in the coming period."

On Wednesday evening, more than 100 mourners, including Masa's classmates, filled the small park where the 17-year-old was killed, leaving dozens of bouquets of flowers and heartfelt messages.

Teenagers stood in silence, stifling sobs into each other's arms, trying to make sense of the tragedy.

Occasionally, a burst of giggling broke out as thoughts turned to fonder memories of their friend, with one classmate remarking: "She would be saying, 'You guys are so stupid crying ... just take the free day off tomorrow'."

Some girls gathered around a phone to play one of Masa's favourite songs.

"I know it's going to be really hard to move on from this," another friend said. "But hopefully as a collective, as a whole year level, we can get past this as long as we are helping one another.

"Masa was Masa ... she was such a wonderful person and we will miss her."

On Thursday morning, the mood at Canterbury Girls Secondary College was sombre as students arrived for school.

Teachers and staff closed ranks around the school ground, and requested privacy.

A number of girls carried bunches of flowers and laid them under a tree on school grounds. The makeshift tribute attracted small groups of students, who consoled each other before walking to class.

- with Konrad Marshall, Allison Worrall, Rania Spooner