This is what I would write:
A bull charged towards the car, at which point I drove away quickly.
I didn't finish work until 10 o'clock, by which time everyone had already gone home.
'At which point' is more specific as to 'the very instant of'.
There's also 'point in time', frequently used during the legalistic questioning of witnesses in the 'Watergate' hearings (when Richard Nixon was President of the United States), and subsequently used often by the man on the street, even when there was no need for specificity of time.