Investigators are trying to piece together the final hours of Marrisa Shen, a 13-year-old girl whose body was found in a park in Burnaby, B.C.

Burnaby RCMP officially declared the case a homicide investigation on Thursday. The girl’s body was found in Burnaby’s Central Park shortly after 1 a.m. Wednesday, approximately six hours after she was last seen at her family home.

Details are scarce regarding her activities within the 12-hour window before she died. Police say they know she spoke to someone on the phone at 5 p.m. Tuesday, and that she did not appear to be in distress during the conversation. Police did not release details about whom she may have been speaking to.

Police are asking anyone who may have seen Shen after 6 p.m. on Tuesday to contact them. At an afternoon news conference Thursday, Cpl. Meghan Foster played a brief surveillance video that shows Shen walking into an apartment building.

The video was captured several hours before Shen’s last known whereabouts. Foster said police are hoping that the video will jar the memories of anyone who may have seen Shen that evening.

In the video, the girl is seen wearing dark shorts and a T-shirt, although the exact colour of her clothes is not clear. Police said she was wearing the same clothes when her body was found.

The body was discovered an hour and a half after a relative of Shen called 911 to report her missing.

“Ms. Shen was a good kid and she is missed dearly by her family,” Foster said.

Shen had just finished her first year at Moscrop Secondary School. She would have started Grade 9 in the fall.

Foster said it is unclear whether Shen was an intended victim of homicide or if it was a random act. No suspects have been identified.

Foster added that the risk to the public is unknown and that residents should “remain vigilant.”

Investigators are urging Burnaby residents to exercise caution, especially when it comes to their children. Kids are encouraged to check in frequently with their parents.

Neighbour Codey Gladson has lived across from Central Park all his life. He said he avoids the area as much as possible.

“Most days I would choose to walk around rather than through it, just because it’s so dark,” he told CTV Vancouver.

A film crew that had been shooting in the area on the night of Shen’s death has also been asked to pack up and get out of the way during the investigation.

The southern section of the park has been cordoned off as part of the investigation.

Area residents say it’s unusual for this kind of incident to occur in the community.