ASPEN, Colo. (CBS4)– Investigators in Aspen are still working on a case where two women collided on a ski run. Only one of them survived.

Investigators said it is considered rare for a skier collision to turn deadly.

READ MORE: Shooting At Aurora Apartment Complex Injures Mom And Child Inside Unit

The collision happened just 15 minutes before Aspen closed on Monday when ski patrol got the call.

Natalie Egelston, 48, from Pennsylvania, was stopped on the Spar Gulch run under some expert terrain called Jackpot when she was struck.

Spar Gulch is a major run for skiers and boarders trying to get down to the base to Gondola Plaza.

READ MORE: Parade, Concerts & More: Juneteenth Celebrations Underway In Denver

Despite the fact that both women were wearing helmets Egelston was unresponsive immediately when ski patrol reached her. She was pronounced dead at the hospital and a coroner’s report shows cause of death as traumatic brain injury.

The Pitkin County Sheriff’s Office is still investigating the speed of the unnamed skier and how the collision happened.

According to the Colorado Skier Safety Act, the person higher up on the hill has the responsibility to avoid people below. When something happens that skier or boarder is at fault.

Aspen Ski Patrol said the woman obeyed the Skier Safety Act by staying at the scene of the collision.

MORE NEWS: Lightning Sparks Over 20 New Wildfires In Extreme Southwest Colorado On Friday

The Skier Safety Act also states if someone is cited it’s only a petty offense that comes with a fine up to $1,000. Officials, however, say the skier who caused the collision could face a hefty civil lawsuit.