"The Small Arms Survey stated that U.S. civilians alone account for 393 million (about 46 percent) of the worldwide total of civilian held firearms" - https://en.wikipedia.org/wiki/Gun_ownership
"Most of them are in the hands of well trained people who are harmless" I am not sure what you base this on, you don't need any training at all to buy a gun, just ~24 - 48 hour waiting period and if you have a concealed carry permit, you can generally walk out with the gun after paying. Depending on the state, training to carry a concealed weapon can take from 2 - 8 hours. Some states don't even require training if you want to open carry your weapon.
In 2010 there were ~20,000 suicides involving a gun. In 2016, there were 11,004 gun homicides. The US leads the world in mass shootings, especially in schools. Accidental gun injuries are most common in homes where guns are kept for self-defense.
https://en.wikipedia.org/wiki/Gun_violence_in_the_United_Sta...
Getting shot by the police is a leading cause of death in young male people of color.
"you might want to figure out who they are and what their agenda is"
Indeed.