BOULDER, Colo. -- A source with the National Transportation Safety Board told the Call7 Investigators that at least three people and possibly up to five died in a collision that involved two small planes and a glider on Saturday afternoon in Boulder County.

The investigator told 7News that a plane was towing a glider northwest of the city of Boulder when another plane flew into the tow line between the aircraft and the glider and severed it.

The two planes crashed, killing all five people on board, according to the source.

At a later news conference, an NTSB investigator said three people died in the crash.

The pilot of the glider, Reuben Bakker, involved in the incident told 7News that he had two passengers on board; a woman and her teenage son, who were onboard for a birthday glider ride.

Bakker also said that the two planes physically collided. He added he piloted the glider through a fireball in the sky after the collision. He said the whole incident happened only a few minutes after takeoff. The glider, which is registered to Mile High Gliding Inc, was able to land safely.

Witnesses described hearing a loud explosion and seeing what looked like fireworks. It didn't take long to realize it was much more.

"We heard a boom, so I looked out the window," said Shano Kelley, who was working in his jewelry shop on Broadway. "We immediately saw two flames."

Kelley said he went to get his camera as his friend continued to watch what happened next.

"She watched two pieces of debris that continued and slammed into the hill over there," Kelley said.

Investigators said the debris field is 1½ miles long. The crash happened about 1:30 p.m.

The main part of a burning plane, a four-seat Cirrus SR20, landed in a large open area. The other plane involved that was towing the glider was a Piper Pawnee PA20. That plane is equipped with one seat.

In video taken by witnesses, a parachute could be seen descending after the collision. The SR20 is equipped with the Ballistic Recovery Systems Cirrus Aircraft Parachute System. It is a large parachute which can be deployed in an emergency to lower the entire aircraft to the ground safely.

"The airplane is falling down and they popped the shoot," said Craig Perkins, who looked up right after the crash happened. "So, the airplane was falling straight down on fire and guys started jumping out of it. Then it hit the ground," he said.

NTSB investigators told 7NEWS it could take a couple of days to locate, document, and then recover the crash evidence. They said it could be months before the investigation is complete and they know a cause of the collision.

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