I could compare this to several things I do - hunting, fishing, competitive shooting, home repair, yard work, but I will take two past lives:
Mechanics and building moving ...
As a mechanic, at the end of each job you scan your work area and check your tool box to make sure there are no missing tools and all removed parts are accounted for;
In building moving, each of us had a truck, trailer or piece of machinery that we were responsible for. Any one of us could look at our responsibility and know if something was missing, and because of uniformity it was possible to question one of the other guy's if something was amiss.
Why doesn't this S.W.A.T. team have a similar check system that says "we don't leave the scene until everyone has accounted for their own gear and the team gear they are responsible for?