A man died Saturday after falling an estimated 100 feet while climbing in Eldorado Canyon State Park.

Witnesses reported that he was climbing the popular Bastille Crack when he fell, and they estimated that he fell approximately 100 feet, said Boulder County Sheriff’s Office Sgt. Andy Smith. Emergency responders were first called around 7:49 p.m.

The man, who has not yet been publicly identified, was reportedly climbing by himself and free soloing.

Eldorado Canyon, southwest of Boulder, has cliffs as high as 700 feet, according to Colorado Parks and Wildlife. It is popular among rock climbers, but people have been seriously injured or killed after falls. The American Alpine Institute rates the formation one of North America’s 50 classic climbs.

In 2012, a 41-year-old man died after falling an estimated 250 feet from the top of the Bastille rock formation.