No it’s not ok that people use them recklessly and kill others but that’s what happens when a dangerous weapon meets opportunity.They were made to kill. It's not okay.
There are people with mental disorders and there are people with anger issues who get access to guns or even own them and bad things happen.
I’m not a gun supporter in the least but I don’t wish to discuss the politics behind the obvious gun problem. It’s not a torch I wish to carry.
It appears that what your brother has done , haunts you.