Gowanda - A family hike in a western New York gorge turned tragic when a mother and father died after falling off a cliff and their 4-year-old son was seriously injured, authorities said.The bodies of Amanda Green, 35, and William Green, 33, both of Buffalo, were discovered along with their injured son Alexander in the Zoar Valley Gorge shortly before 13:00 on Sunday, Erie County Sheriff Timothy Howard said. Rescuers found the couple's 7-year-old son, Jacob, walking nearby.The 4-year-old was airlifted to a Buffalo hospital, where he was listed in critical condition. His brother was also taken to the hospital to be checked out for unspecified non-life-threatening injuries.Authorities believe the two adults and child fell about 6m down a steep cliff but are not sure what caused the fall. Police continue to investigate.Hikers came upon the adults' bodies, Howard said."The first two hikers who found the bodies did not have a cellphone," Howard said. "They flagged down a third hiker who made the call."Rescue crews found sneakers that were too large for the 4-year-old and began a search. Eventually, the elder boy met up with rescue personnel, officials said.The Zoar Valley, on the Erie-Cattaraugus county line 56km south of Buffalo, is a popular hiking and kayaking spot, with scenic cliffs as high as 122m and the whitewater Cattaraugus Creek running through the gorge.The gorge has been the scene of several rescue operations in recent years after hikers got hurt or became lost.