Incidents like this are unfortunately not infrequent, and are usually due to poor prisoner search and handling procedures.
There have been cases recently where handcuffed individuals, improperly searched, had produced concealed firearms and either shot arresting officers or themselves.
In one video we were shown for training purposes, a non-resisting drunk was left alone in the booking cell for a few minutes... The video shows him producing a full-sized .45 automatic from the small of his back and shooting himself....
We disarm before handling any prisoner at the station, putting our handguns in locked boxes, and search the prisoner thoroughly before starting any booking procedure. This is what's supposed to be done...
Coppers get lazy, the subject is apparently cooperative, or extremely filthy....shortcuts are taken and tragedies occur.