The pair, aged 15 and 16, were arrested in the ACT on Friday morning and it is expected they will be extradited to NSW on Saturday after allegedly stabbing Caltex service station attendant Zeeshan Akbar, 29, to death at Queanbeyan.

NSW Police Force Deputy Commissioner Catherine Burns said there was some evidence the spree could be terror-related or linked to drugs.

"We have two teenagers in custody and sufficient information to believe the actions of one of those teenagers may be related to terrorism," she said.

"That information comes from physical evidence at the scene and other sources."

Prime Minister Malcolm Turnbull said the circumstances of the stabbing warranted the involvement of the Joint Counter-Terrorism Team.

Friends paid tribute to Mr Akbar, a Muslim man who was hoping to get his Australian citizenship.

His friends had posted photos online of him celebrating New Year's Eve at Sydney Harbour and sightseeing at the Blue Mountains and Collins Beach in Manly.

"This is really an unbearable loss for his family," one friend posted.

It is believed the ordeal began about 8.10pm on Thursday with the alleged attempted robbery of the Vintage Cellars liquor store in Oaks Estate.

After fleeing the store empty handed the two teens allegedly embarked on a trail of destruction that included:

Speaking on condition of anonymity, the first victim allegedly approached by the two teenagers described the chilling signs of carnage to come.

The man had just finished a shift at the Oaks Estate liquor store on Thursday night when they approached him out of the darkness.

"One of them was holding something behind his back like they wanted me to think he had a gun," he said.

"He said three times, 'Give me the cash'."

CCTV footage seen by Fairfax Media shows a brief scuffle, before the assailants flee empty handed.

"To think that a man was killed later that night. It's too scary to even think about man.

"I could have been killed."

Mr Akbar would not be so lucky when the pair allegedly entered a Caltex store on Bungendore Road, Queanbeyan just three hours later.

Police alleged the teenagers were let into the store by Mr Akbar, before they set upon him in a "horrific" stabbing.

He was found by a workmate about 11.55pm and died a short time later, Monaro police commander Superintendent Rod Smith said.

It is alleged the teens took the cash register before fleeing.

In the hours leading up to the fatal stabbing, police alleged the boys violently attacked a man in Queanbeyan's Apex Park.

"They approached a man in the park and it is alleged they made some demands of him before hitting him over the head with a beer bottle.

"They caused him significant facial injuries."

After that, they allegedly forced their way into a property on Stornaway Road and bludgeoned a man with a tyre iron.

Their final act came about 6.20am on Friday, when they allegedly stabbed a man in the stomach and stole his silver Ford Falcon.

A witness told The Canberra Times she peered out her window to see a man lying in the middle of the street surrounded by police cars on Southwell Place near Barracks Flat Drive.

It is understood the two boys fled the scene in the stolen car, evading police attempts to stop them as they travelled through Queanbeyan.

They were arrested a short while later by ACT police about 6.35am, on the Monaro Highway south of Isabella Plains.

NSW Police have begun extradition proceedings to bring the teenagers back across the border, with the pair expected to face court in the ACT on Saturday morning.

Prime Minister Turnbull said his thoughts were with all those affected by the violence.

"Our condolences go to the family of the victim," he said.

"We send our prayers and best wishes to the two other victims of that evening."

ACT Police and Emergency Services Minister Mick Gentleman said police believed the incident was an isolated matter, and there was no ongoing threat to the community.

- with Rachel Olding and Megan Levy