A beloved Hudson Valley teacher fell to his death while on vacation.

On Sunday, Marco Dees, 33, tragically died while rock-climbing at Grand Teton National Park in Wyoming.

Dees was an adjunct professor at Vassar College in their Philosophy department. Last year he taught “Reality, Knowledge & Morality” and “Logic.” He previously taught at Bard.

"Just 33 years old, Professor Dees was at the start of what promised to be a full and productive career," Vassar College President Elizabeth H. Bradley said in a message to the college. "Professor Dees’s areas of expertise included metaphysics, epistemology, philosophy of science, and philosophy of physics."

Dees was rock-climbing in Wyoming with 2015 Vassar College graduate Grace Mooney.

"Marco was an accomplished rock climber, outdoorsman, and mountaineer who died doing what he loved most,” Mooney said.

Dees was Mooney's rock-climbing mentor. The pair rock-climbed in the Hudson Valley before planning a trip to Wyoming, according to the Wisconsin State Journal.

An improperly rigged ATC belay device likely caused Dees to fall 300-feet to his death, the Jackson Hole News and Guide reports.

“We think that he accidentally only clipped one of the strands through the device into his carabiner, and didn’t notice it until he leaned back,” Jenny Lake Climbing Ranger Ryan Schuster told the Jackson Hole News and Guide.

Dees fatal fall also took Mooney's rappelling rope. She hung to the mountain for over 12 hours before she was rescued.

A remembrance at Vassar will be planned for the fall.