Since the explosion of mobile technology and home entertainment system in post 2008, more and more people are staying at home than being out in public. This has caused an epidemic of big proportions of anti social behavior on our children and young adults. Instead of young people being influenced by their friends they are now influenced by the internet often growing radical ideas and behavior. To an extreme they turn into violence.This explains why there is an explosion in mass shooting starting from the early 2000's.
I have seen this problem in person myself. When im out in public most people are rather on their phones than talking to one another. More people socialize better thru social media than socializing in person. This is a very scary situation for the u.s. as technology keeps advancing more people will enclose themselves from society. The situation will get much much worse.