For many decades we have had essentially the same gun laws. We have had more or less the same racial issues. We have had "income inequality" since income has been a thing. Some will insist these things have gotten worse, but they haven't. What's gotten worse is the manifestation of human nature.
The common thread you'll find with every supposedly shocking act of violence - whether it's Boston, Sandy Hook, San Bernardino, Orlando, Ford Hood, Columbine, Kalamazoo, Baltimore or Dallas - is pure evil. Someone in each incident made a conscious decision to harm others, in some cases many others. Whether the killers were jihadists or racial activists or deranged Americans, they all decided to kill. Their guns didn't tell them to do it. Donald Trump didn't tell them to do it.