Webster defines killing as doing something which puts an end to or extinguishes life, to cause one to (cease to) exist or cease operating, and/or to deprive one of life.
Automobile accidents which kill, cancer and/or heart attacks which can disable anyone in just a split moment of time could perhaps be placed in the life-killer category.
A far more far-reaching deadly threat in the taking elements of life might be verbal utilization of just a few spoken words, i.e. criticism.