 On September 16, 1976 while jogging alongside Yerevan Lake with his brother Kamo, also a finswimmer, Karapetyan had just completed his usual distance of when he heard the sound of a crash and saw a sinking trolleybus which had gone out of control and fallen from a dam wall.The trolleybus lay at the bottom of the reservoir some 25 metres (80 ft) offshore at a depth of 10 metres (33 ft).Karapetyan swam to it and, despite conditions of almost zero visibility, due to the silt rising from the bottom, broke the back window with his legs.