Dear Health,
I am not a bible thumper. This is not the parshah of the din of rodef. See the latter half of eight perek of sanhedrin.
You can not assume things in life and death matters. [This may be a major earth shattering chiddush to you.] You have to examine the factors carefully.
In many Police departments they do only half of their job. Eventually we should give them better training, or find private alternatives.