They mention Epic specifically, but a majority of hospital systems rely on Epic.
I’ve wondered how long this would take, and what effect it would have during a (not-even-mass) casualty event. The more paranoid might see events like this a probing attempt into how far one can go in infrastructure chaos-people still think “power grid” or “water”, but “medical” - as Gaza has shown - is just as intricately linked to all that.