Do you know what a rubber bullet is? It is NOT what its name implies. It's a rubber-coated steel cylinder, meant to be shot only at legs and feet, and only from a distance of not less than 40 meters, and only after all other riot control measures have proven ineffective. A hit in ANY vital area, such as the head or chest, is likely to be just as lethal as a regular bullet. So no matter which was used, the intention was to kill.
Islamist militants attack African Union base in southern Somalia (Reuters)
from the article: PA accuses Israel of killing Palestinian teens 'in cold blood'