Police have a cause of death for Barrie, Ont. teen Brandon Crisp but the full story behind his final days might never be known, suggests a Barrie police officer.

"The investigators from OPP (Ontario Provincial Police) and Barrie are working together to piece together a timeline and help us understand what led Brandon to where he was, what occurred in the hours leading up to his death," Sgt. Dave Goodbrand told ctvtoronto.ca on Saturday.

"And a lot of those questions might not be answered, but everybody's doing what they can to look into this and see what they can determine."

However, foul play has been ruled out, he said.

Autopsy results suggest Crisp died from chest injuries, possibly sustained in a fall from a tree. The 15-year-old went missing from Thanksgiving Day until hunters discovered his body on Wednesday.

"The cause of the death was determined through medical examination to be as a result of injuries to the chest area that are consistent with a fall from a tree," the police said Saturday in a news release.

Goodbrand said police can't answer yet how far Brandon might have fallen, adding that will be one question addressed in the ongoing investigation.

Brandon left home after he got into an argument on Oct. 13 with his parents, Steve and Angelika, about his constant Xbox video game playing. He was obsessed with the combat game "Call of Duty 4: Modern Warfare." His family never heard from him again.

Police launched boat, helicopter and foot searches in the areas where they thought Brandon may have headed, including to the rail trail where he was last seen alive. Volunteers supplemented the police search by expanding the area.

Police also restarted the search last weekend, canvassing drivers and others in the area where Brandon was last seen to see if anyone knew something that might help find the youth.

On Wednesday, locals out deer hunting stumbled upon a body matching Brandon's description in a wooded area east of Barrie, more than three weeks after he first disappeared. The body was outside the search area.

The hunters have reportedly said they don't think Brandon's body had been there for three weeks.

"We have never released details that said he's been there three weeks. We don't even know the amount of time he was there," Goodbrand said.

The medical examiners will release information as to the time of death if they can determine it, but details on the body's condition won't be released out of respect to Brandon's family, he said.

Some media reports speculated earlier that Brandon might have succumbed to hypothermia, a dangerous lowering of the body's core temperature that can eventually lead to death.

Goodbrand said that might have been based on earlier conjecture that it would have been difficult for Brandon to survive outdoors under chilly conditions, given the limited clothing he had with him.

"Obviously we based our information based on the post-mortem," he said.

The parents learned about the autopsy's results on Friday night.

"It's a very difficult time for them, they're taking it very hard," Goodbrand said. "This is tragic news for everybody involved."

Steve and Angelika are expected to make a public statement in the coming days.

They will hold a funeral for their son at 10 a.m. on Friday at St. Mary's Church in Barrie.

With files from The Canadian Press