Until widespread testing is done, we really aren't getting enough data to see a more accurate picture of this virus and how deadly it really is.
But for now, for the small samples that have been done, it is looking like the risk for people under 45 with no pre-existing heath conditions the death rate is extremely low. Most people in that demographic who get infected have mild to no symptoms at all.
But many of the people with severe cases, the virus doesn't just cause damage to their lungs, but sometimes also their heart, brain and kidneys.
Edit; I meant to say the virus triggers an overactive immune response/cytokine storm that damages other organs in the body