Around 9:30 p.m. Saturday, I think.
The article says the Saturday attack was the first in “recent memory”. I’d like to know how far back you’d have to go to find the previous such attack on a BART train. My guess is this is in fact the first *ever* with a group of attackers that large, and that the “in recent memory” bit is just there to downplay the fact that this is unprecedented. Could be wrong of course.