Story highlights

Two teenagers decided to use runoff to slide down Stone Mountain outside Atlanta

Their plan went awry and both were injured; rescue crews took them to hospitals

The two teens were lost in a restricted area on the back side of the mountain

CNN  — 

An outing by church youth group went awry in a Georgia historical park Tuesday when two teenagers who thought they could use watery runoff to slide down a mountain ended up hurt, authorities said.

An 18-year-old man suffered moderate to severe injuries, and a helicopter took him to an Atlanta hospital from Stone Mountain, a popular park outside Atlanta, said Norman Augustin, deputy chief of DeKalb County Fire and Rescue.

A 17-year-old boy was severely injured and taken by vehicle to Gwinnett Medical Center, Augustin said.

The two teenagers were in a restricted area on the back side of the mountain, and their plan to slide down a granite face didn’t work, said John Bankhead of Stone Mountain Park Police.

The two teenagers tumbled down the mountain about 70 to 100 yards into a ravine next to a pond, Augustin said.

A father and his 12-year-old son were accompanying the two teenagers on a trail when they got lost and ended up on the back side of the mountain, Augustin said.

The father explained that the 18-year-old intentionally slid down the mountain, and the 17-year-old boy followed and tried to help him, Augustin said. Runoff from rain descends from the summit and makes the granite surface slippery, authorities said.

The father ran down the mountain and sought help, Bankhead said.

No charges will be filed, Bankhead said. Augustin didn’t have details on the church group affiliation, he said.

CNN’s Devon Sayers contributed to this report.