This paper reports the lightning-caused tragedy on October 5th, 2014, when 11 Colombian Indigenous inhabitants died and 15 were seriously injured inside an Unguma, a ceremonial house constructed with traditional methods. The accident scenario and the possible interaction mechanism that produced several traumata in the indigenous men are described. The ground potential rise inside the Unguma and the energy absorbed by a simulated human body placed on the floor surface at eleven different positions and distance spans from the possible lightning impact point are calculated. The calculation was performed through electromagnetic numerical simulations of a lightning direct impact on a simplified model. A parametric analysis was performed with four soil resistivities.