My younger son was a school social worker just outside of Binghamton for years. He knew, for example, that the guy who shot the people at the store in Buffalo had threatened to do a school shooting during his class's graduation. The kid came from a seemingly "normal" -- whatever that may be -- middle class family. He said that he had been influenced by the internet, likely as an attempt to shift some of the blame, I think.
There are a heck of a lot of kids growing up in single parent families. My son worked with kids who had a parent incarcerated in county jail or state prison. A few had both parents incarcerated. Now, there are many, many outstanding single parent families. There definitely are. But there are a lot that are not, due to other factors such as poverty, addiction, etc. There are neighborhoods without positive role models.
Some of these issues will take more than a generation to address and heal -- if this country were to invest in serious efforts. I remember towards the end of his life, former two-time heavyweight champion Big George Foreman said he remembered a time when this country cared about poverty. (My son contacted George, who put on a free showing of his movie for the kids!)