I'm not sure if you all caught this, but professor Jacobs suggested that some "mechanisms" could be put in place that would allow citizens to alert police before something like this happened.
Some possibilities: How about a database that allowed law enforcement to comb your medical records, internet traffic, e-mail and voice communications that would suggest to them to a possible attack imminent- all without a warrant? Or how about your neighbors reporting you to the police because they don't like the way you keep your yard? Of course every effort would be made to protect your privacy and they would ensure that none of us would be detained unless there was a "very good reason."
Be vigilant.....