To be fair the legal use of lethal force involves an intent to stop the perpetrator, not to kill him. You can very much get yourself convicted of murder in what would otherwise be a self defense case if a jury is convinced you were looking to kill someone intentionally. That’s why among other reasons you should call for an ambulance immediately and politely keep your mouth shut until you speak with your lawyer.

The first part is true.

Murder doesn't require a gun, murder isn't a universally essential act, and guns don't have to shoot. Knife crime murder is epidemic in some countries. Guns can also be decorations, used for sport of marksmanship, or insurance policies against home invasion; they are inanimate objects without intent of their own. Killing is occasionally essential when all other means of self-defense have been thoroughly exhausted and someone else is intent on great bodily harm or murder that cannot otherwise be prevented with lesser available force or evasion.