Second Lt. Erin Edwards with the Joint Rescue Coordination Centre in Victoria said crews have recovered the bodies of the pilots and passengers from both aircraft which fell into the area of Nairn Falls Provincial Park.
A man who witnessed the immediate aftermath of the crash described hearing a "big bang" and then seeing a glider spiral down to the ground.
Dan Wall, who was on a bike trail near the park campground, about 50 kilometres north of Whistler, said the trees were so tall that he couldn't properly see what happened in the air.
However, after the loud noise, he and his companions saw a plane moving over the trees, and a glider falling.
"The glider hit the ground. You could hear it. You could see the debris in the air, so people started taking cover," he said.
The campground was fully occupied at the time. No campers were hurt, although an RCMP spokesman said debris fell within six metres of some campers.
One of Wall's companions is a search-and-rescue volunteer, so the group headed towards the wreck of the glider. The glider came down just outside the campground, near a park maintenance area.
Wall stood back, but said there was visible fire, and witnesses grabbed small fire extinguishers from the maintenance area and started putting it out.
He did not see anyone being pulled from the gliders, but also said he didn't want to get in the way and didn't go very close.
"The glider scene was... it was pretty brutal," he said.
Wall said he did not know what happened to the small plane that he saw fly overhead after hearing the initial bang.
"Apparently, from what we heard from firefighters that arrived on scene, the plane had continued on and actually crash-landed on the opposite side of Green River, which runs alongside the campground," Wall said.
Officials with CFB Comox confirmed that four people and a dog had died as a result of the mid-air collision between a two-seat glider and a Cessna 150. The Cessna was from 100 Mile House, a community northeast of Whistler.
Officials do not know if the plane was towing the glider.
Police have notified the next of kin, but the victims' names have not been released.
The Transportation Safety Board confirmed it has sent investigators to the crash sites, and will be launching an investigation.