There are generally specific policies and training to try to ensure this type of mistaken tool deployments don’t happen.
It’s not just law enforcement but other professions too. Just off the top of my head how many times are surgical tools or bandages left inside a patient despite a knowledge of it happening many times before and specific protocols involving counting of tools/bandages. Or a mechanic that doesn’t tighten the lug nuts on a wheel(s) and letting the customer drive off.
Sadly humans are going to human sometimes and make mistakes despite policy and training. Sadly mistakes like this one involve serious physical injury and death.