Police have released surveillance video of 13-year-old Marrisa Shen taken on Tuesday, hours before she was killed.

The Integrated Homicide Investigation Team said the video depicts Shen entering an apartment building located blocks from Burnaby's Central Park, where her body was discovered early Wednesday morning.

Authorities are hoping someone will recognize Shen and help police fill in the gaps between her last known sighting and the time of her death.

"We'd like for people to recognize her walk, how she appeared to people who may have been driving by that may actually realize that they saw her," Cpl. Meghan Foster said.

Shen's outfit, which includes dark shorts and a dark T-shirt, is believed to be the same one she was wearing when her young life was cut short.

Foster said police have also confirmed what they have suspected since early Wednesday: that Shen was the victim of a homicide. It's still unclear whether she was targeted or killed at random.

"Those public safety issues are still unknown and we ask people to remain vigilant," Foster said.

Earlier on Thursday, IHIT narrowed down the timeline for Shen's death. Although investigators initially said no one had seen Shen from 1 p.m. Tuesday to the time her body was discovered at 1:30 a.m. Wednesday, new information reveals she was spotted leaving home at 6 p.m.

Foster said the teenager did not appear to be in distress at the time.

Few details about the deceased have been shared by authorities, but IHIT described her as a "good kid."

"She's missed dearly by her family right now. They're in the initial stages of grieving, and we're working and doing the best we can to find those responsible," Foster said.

Investigators have yet to identify a suspect or determine a possible motive for her killing.

Shen's body was discovered in a heavily wooded area of Central Park about two hours after she was reported missing.

Police were still scouring the 90-hecatre green space on Thursday, and could not confirm when they would be finished. Several areas remained behind caution tape.

The shocking crime has left some residents of the area, particularly those with young children, feeling unsafe.

"It's not a good feeling. Don't know [whether] the person would be lurking still around the neighbourhood," said Darcel Collinson.

IHIT said it has already received several tips from the public, but there is still much work to do. Dozens of officers are working on the case, including members of the Vancouver Police Department.

Anyone with information can contact the IHIT tip line at 1-877-551-IHIT, or Crime Stoppers at 1-800-222-8477.  

With files from CTV's David Molko, Alex Turner and Ben Miljure