You are right.
Even in law, taking a life in self-defence is permissible. Only if it was the only way to save one's life or prevent serious injury.

It might sound easy to cock a gun and blow off a person's brains, but when you are faced with the situation, you might think of a means of escape first. And might hate yourself for ending their lives even if you did so in self-defence.

Most governments can't execute capital offenders anymore. The last time the any of our country's leaders gave such approval was in 2016 or thereabout. They'd rather leave them to spend the rest of their lives in prison. Wouldn't even approve euthanasia, even if it was the only option to save a life.

Those who are capable of cocking a gun are often those in the military who are accustomed to killing, emphasis on those accustomed. And also individuals who believe that death silences a person. I don't think I fall under any of these categories. 😭