Rachel Pernosky was reported missing by her family late Saturday night, from her home in Mission, B.C.
Her body was spotted Tuesday evening, tossed down a steep embankment in Chilliwack, about 44 kilometres away from her home.
A search and rescue team was called in to retrieve Pernosky's body after a passerby saw it from the road above and called police.
The discovery came after days of exhaustive searches by family, friends and police.
"She was eighteen years old, she was a mom herself of a very young child," RCMP spokeswoman Sgt. Jennifer Pound said at a news conference Wednesday.
"This has left a hole in her family and it's left a little boy without a mom," Pound said. "If anybody has any information, we're asking them to please come forward."
An avid user of social media, friends and family became concerned Saturday after Pernosky's Facebook and Twitter accounts fell silent.
Insp. Richard Konarski, with the RCMP's detachment in Mission, said police initially launched a 25-officer search effort but hadn't anticipated the case to result in homicide.
"I think (for) anyone who's a parent, the thought of losing a child is probably the worst thing you can possibly imagine," Konarski said.
With no history of criminal activity or running away, police became suspicious when they found Pernosky's belongings had been left at home the night she disappeared — among them her purse, credit cards and cellphone. Police said there were no signs of forced entry.
The teen's one-year-old son Marco was not with his mother at the time of her disappearance, Pound said at the news conference.
The baby is currently in the custody of his biological father, Pound said.
The father of the child is "not a suspect," Pound stated.
While the murder appears to be targeted, Pound said police do not yet have any suspects in custody, or a definitive motive.
They are however, in the process of interviewing a number of people, Pound said.
It's also unclear if the young woman was murdered at the scene, or if her body was just dumped there, the officer said.
She added the social media websites Pernosky frequented may be key in finding the young mother's killer.
The RCMP has cordoned off the area where Pernosky's body was found. Pound said the results of an autopsy are expected Thursday.
Those who knew the petite, green-eyed Pernosky have been left to grieve her short life.
"Rachel ... had a laugh like no other that could brighten anyone's mood, " said her friend Rachel Allard.
"Rachel was a wonderful girl," said Allard, whose older brother befriended Pernosky during their first year at École Mission Secondary School. "(She) was always like a big sister to me, always kept her head high through every situation."
"Everybody who knew her is devastated," Allard said, communicating via a private Facebook message.
While she wasn't out on foot searching for Pernosky, Allard said she told everyone she knew of the disappearance.
The word spread like wild fire on social media, where a Facebook group searching for the lost teen grew to 2,800 strong. Now, the group's wall is a growing epitaph of Pernosky's life.
Friends and family will hold a candle-lighting ceremony in at Heritage Park in Chilliwack on Thursday night, and a benefit concert on Friday.