as @thespybrief says, there are almost always signs. there were glaring ones here.
Her coworkers who reported her 100% did the right thing.
nbcnews.com/news/us-news/o… via @nbcnews
starting with:
why was she able to buy an AK-47?
why did her mother allow her to keep one in the house?
"The [school] told investigators that she had been suspended for bringing a knife to school and having a swastika symbol on some of her belongings."