The info graphic you posted shows that shooting at vicious dogs works! Since cops are armed (and they do not hesitate to use them), no cop has died at the fangs of the canines. However, here is the static on dogs killing humans in the US:
2013 - 31 unarmed people killed. No cops were killed.
2012 - 35 unarmed people killed. No cops were killed.
2011 - 33 unarmed people killed. No cops were killed.
2010 - 37 unarmed people killed. No cops were killed.
I see the pattern.
If my child was lost, would I want the cops to look everywhere they could think to look? Yes.