Well that’s utterly false on it’s face.
Humans have been and continue killing other humans without firearms for as long as we’ve had humans.
You don’t need a gun to commit a murder.
It is also absolutely impossible to remove all the guns from the United states that are in civilian hands.
We have a thriving black market in guns among the criminal class that already has somewhere in the neighborhood of 100 million guns circulating it and open borders that endure a steady supply for the life of this country.