The family of Chinese teenager Wei Liao is preparing to travel to Australia following her "horrific" death at the hands of a knife-wielding intruder in Waterloo on Sunday.

The 18-year-old Taylors College student was killed when she fell naked onto concrete from the balcony of the third storey McEvoy Street apartment she shared with her boyfriend and two other flatmates.

Her boyfriend, 19-year-old Chris Han, fractured both legs, his pelvis and his back when he tumbled down shortly after Ms Wei, about 1.45pm.

It is believed the couple were made to perform sex acts at knife point during an attack that lasted an hour after their assailant forced his way into their building.

Today, management at Taylors College in Waterloo were working with Chinese consular officials to organise passports and visas so the families of both victims could come to Australia.

Counsellors had also been called in to speak with the friends and former teachers of the "quiet, attractive" teenager.

In a written statement the college's management said the 18-year-old was a "highly respected and regarded student" at the Waterloo campus.

"Along with the rest of the community, the tragic and dreadful circumstances have shocked and distressed us all," the statement read.

Peter Price, the managing director of Taylors College in Australasia, said Ms Wei had moved to Australia from China with hopes of studying at University of Sydney.

She and Mr Han had both enrolled in a pre-tertiary "transition program" designed to ease their way into university.

Mr Price said the college was working with Chinese consular officials to organise passports and visas for Ms Wei's family, who were travelling out from China.

Police would not release any further information about their investigation into the attack, which has been described as a horrific and opportunistic home invasion.

Ms Wei and Mr Han's 20-year-old Chinese flatmate and their female friend were also in the apartment at the time.

The alleged intruder, a man police described as aged about 30 with a dark complexion, followed a female friend of the victims through the unit block's security entry at about 12.35pm.

Once in the lift, the man held a knife to the woman's throat and forced her to take him up to the flat, police said.

Little more than an hour later, Ms Wei had fallen naked to her death from the unit balcony. Witnesses said Mr Han fell moments later and lay on the ground groaning in pain.

It is understood Mr Han told paramedics a male intruder had made the pair jump from the balcony

"He was still coherent after the jump and was trying to tell them what happened," a source, who asked not to be named, said.

"They were forced to do sexual acts and then forced to jump off the balcony. That's why they were naked."

Police would not confirm Mr Han's version of events but did not rule out sexual assault.

Redfern's local area commander, Luke Freudenstein, believed the pair had been climbing to safety on the balcony below when they fell. "We have no information before us at this time that indicates they were forced to jump," he said.

Police have asked for people who may have seen the man in the area to contact them. Security camera footage was also being examined.