Mystery solved by lanceman at https://reopenkennedycase.forumotion.net/ This is a court clerk being taken hostage at the Jack Ruby trial, as other films and reports show. My confusion perhaps caused by the way Mr Alyea accreted clips of film onto a reel over time.
Anyone know anything about the incident at the end of Tom Alyea's film where a man appears to take a woman hostage at gunpoint, exit the TSBD, and proceed into the intersection of Elm and Houston?