In the case of fatal falls, the injuries a person suffers will depend on how fast they were falling, the surface they landed on, and which part of the body first impacted it. The terminal velocity (fastest falling speed) of a human in a “stable, belly to earth position,” averages out at around 120 mph, and those in a head-down position travel faster — up to about 180 mph says Speed Skydiving.

As Mosaic reports, in 2007, the Moreno brothers, who worked as Manhattan window cleaners fell, 472 feet from the scaffolding on Solow Tower when their support gave way. Edgar Moreno struck fencing as he fell and was killed on impact, but Alcides Moreno survived after extensive medical care. He required 24 pints of blood before he would stabilize. He broke both legs, one foot, one arm, and multiple ribs, as well as suffering awful damage to several organs. It was remarkable that he lived, and it’s suggested that he did so only because certain factors (such as the platform taking some of the brunt of the impact) reduced the force of the collision. Their terrifying fall lasted only six seconds.

ABC Science explains that it’s the force of such sudden deceleration that causes such extensive damage. Falling at around 124 mph, an immediate stop means that at the point of impact, the internal organs weigh around 7,500 times more than usual in that brief instant. The pressure of this can tear the aorta away from the heart, rupture every blood vessel in the body, and be all-around very, very fatal indeed.