This is far from the first security failure associated with this particular facility. A quick google brings up quite a few warnings of exactly this kind of threat that have been raised over the past couple of years.
This shows how prominant some of these concerns have been.
Treatment of disabled offenders is obviously an incredibly problematic issue and innovative approaches are important, but not when they pose a threat to unsuspecting members of the public. Basically anything DHS touch turns to shit too, as that place is full of the most despicably useless bureaucrats imaginable. Their incompetence knows no bounds, and it is a fairly safe bet that they have been aware of these exact issues for years and done nothing about it. Hopefully somebody does launch a law suit. I would love to go after them for their ongoing child protection failures, but unfortunately it is incredibly difficult to make anything stick.