Police began investigating the deaths of 19-year-old Craig Wood and 17-year-old Kendall Moore on May 18th.
They say the two were at an outdoor party when the vehicle they were in entered a lake about 42 kilometres west of Prince George.
Investigators focused on forensic evidence, vehicle inspections, interviews and autopsies.
Police say they believe substance abuse was a direct factor in the deaths and the actions of the male driver led to the death of the female.
They say their investigation will end as a homicide-suicide.
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