Something I am unsure of about America

I have read this:
"The right to bear arms" is the right to possess and carry weapons, a concept rooted in English history and enshrined in the United States as the Second Amendment, which allows people to have arms for self-defense and other purposes, subject to regulations.

What are the regulations? I ask because if someone can just gun down a thirty one years old as they disagree with his rhetoric how are guns and the right to bear arms working? Surely the fact the Framers didn’t include it in the Original Constitution means they didn’t want people killing other people adhoc.

Here in Italy 🇮🇹 I am privileged to have a concealed weapon because of whom my father is. But it is PURELY for self defence, and the defence of my daughter who is still a minor.

I read somewhere too that the police in one town went on strike and everyone wore a gun and they say crime was almost non existent. When the Amendment was added was this historically the thought of the legislators because there were a spate of killings?