Tall fir trees block out the ambient light, and there is true silence. The huge Metrotown shopping complex and a bristling skyscraper district are five minutes away in this Vancouver satellite city, but you would never know it. The trail is paved, but on this moonless night it feels like deep forest, cool and dank and claustrophobic.

Vancouver police have revealed little about the killing of Marrisa Shen, a 13-year-old schoolgirl who lived nearby. Her body was found in brush somewhere off the trail at 1.10am last Wednesday, less than two hours after she was reported missing. Officers will not say exactly where Marrisa’s body was found, nor have they explained the specific circumstances that led to its so-swift discovery.

But they have issued a warning.

“The risk to the public remains unknown – but we ask that the public remain vigilant,” said Corporal Meghan Foster of Metro Vancouver’s Integrated Homicide Investigation Team, in a press briefing last Thursday.

Foster said Marrisa spoke with her family by phone at 5pm last Tuesday, July 18. Surveillance footage that allowed police to narrow the time frame of her killing shows her entering and leaving an apartment building. A snippet was released by police to show the clothes she was wearing at the time – a dark t-shirt with a large colourful design on the front, dark shorts and dark Nike sneakers. Her long hair is unrestrained. She appears to be carrying only her phone. At 6.02pm, police said the footage showed her for the last time, exiting the building.

Anyone who saw Marrisa after then has been asked to contact police.

“The evidence doesn’t indicate whether Miss Shen was the intended victim of this homicide, or if the homicide was a random act,” said Foster.

“Investigators are working tirelessly to gather and review evidence. No stone will be left unturned, and we ask that anyone with information contact police so that we can apprehend those responsible, and hold them accountable.”

But details released by IHIT have been scant; Foster would not even say whether Marrisa made her final phone call or if she received it, nor whether the building Marrisa is seen entering then leaving is her family home. The cause of death has not been described - pending a report from the coroner - and there has been no attempt to clarify the exact circumstances that led to Marrisa’s body being found so quickly. The search for Marrisa was launched “immediately” by the Burnaby detachment of the Royal Canadian Mounted Police after they were contacted late on Monday night, IHIT said in its initial press release.

There have been at least 30 homicides in British Columbia’s Lower Mainland this year, but 20 or so have been targeted victims, with many related to the region’s gang scene. Others have stemmed from street altercations, or domestic violence. Of these, some remain unsolved. But Marrisa’s killing stands alone for the level of mystery surrounding the case, her young age, and the public grief.

There is a makeshift memorial to Shen on a patch of concrete near the entrance to the trail, overflowing now with flowers and cards and stuffed toys – a bear, a dog, a Hello Kitty doll.

The votives in her honour have all burned out, but a battery-powered candle flickers on.

Among the tributes is a spiral-bound notebook from Burnaby’s Moscrop Secondary School, where Shen had been due to enter ninth grade after the summer holidays. A large poster – “to Marrisa with love” – is filled with handwritten messages in English and Chinese, some from strangers, some from friends.

“I’m so glad I got to know you, even though it wasn’t for long.”

“God loves you.”

“You matter to all of us. We won’t let you down. We won’t stop until we find out what happened to you.”

Police patrols have been stepped up around the park.

But after midnight on the trail where Marrisa likely took her final journey, it is still and quiet.

Can the city really be so close? Look up through the trees, and the stars shine bright between the silhouetted boughs. And the illusion of wilderness is complete.

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Anyone with information is asked to contact the IHIT Information Line in Canada at 1-877-551-IHIT (4448), or by email at [email protected]. Should you wish to remain anonymous, please contact Crime Stoppers by phone at 1-800-222-TIPS (8477).

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The Hongcouver blog is devoted to the hybrid culture of its namesake cities: Hong Kong and Vancouver. All story ideas and comments are welcome. Connect with me by email [email protected] or on Twitter, @ianjamesyoung70 .