Witnesses who were at the Starbucks near Hastings Street and Kensington Avenue when the incident happened told CBC News it started outside — over a cigarette butt tossed from a car.
"The woman tossed a cigarette out the window and he [Page-Vincelli] picked it up and he threw it back at her," said Michael Zimeras, who was one of the witnesses outside the coffee shop at the time.
The woman went inside a nearby bank and came out with a man, and the pair followed Page-Vincelli into Starbucks.
"Two minutes later they came out," said Zimeras.
According to witnesses inside the coffee shop, who declined to be identified, Page-Vincelli was punched and fell, hitting his head on the counter.
Burnaby RCMP were called to the scene, and found the victim "suffering injuries," according to the Integrated Homicide Investigation Team, which is now in charge of the case.
Page-Vincelli was taken to hospital, but died July 15.
"IHIT investigators are diligently pursuing leads and advancing the investigation," said Cpl. Meghan Foster in a statement.
"Investigators believe there are no concerns relating to public safety."
No charges have been laid in the young man's death, and officials are not identifying any of the people involved.