The Saturday attack was the only one I ever heard of on a BART train since BART began carrying passengers in 1972. Therefore, the first time was also the last time, i.e. Saturday evening.
Are you from the Bay area by chance and familiar with the goings on of BART? This seems like a significant first if it is in fact a first. I was hoping the article would have comments to see how the locals were reacting but no comments.