Being There: Oswald @Tippit
Sticks to him like ugly on a moose
Brewer and others were just observers along the way as the little prick passed through their lives, however briefly.
Brewer: Saw/Said what he saw.
Quaker Ruth: Saw the uninvited Oswald at her home on the eve of the assassination where there was a rifle, and then there wasn't.
Both contributed. Can't see why they would need to see a crime being committed in order to simply report what they saw. They were just part of Oswald's baggage along the way to his becoming a somebody.