Well ya see it's like this. Sam Cassidy expressed HATRED for his workplace in notes discovered almost 5 years ago. What was done then? Either nothing or not enough apparently.
Authorities found a black memo book filled with hatred toward the VALLEY TRANSIT AUTHORITY when they searched his house after the massacre. They also found books about TERRORISM FEAR and MANIFESTOS.
So they had a head's up on the crackpot nutjob almost FIVE YEARS AGO and well you can see what good it did.