Go to an indoor range and spend some money renting handguns and shooting them.
Fact: The neatest homicide I ever worked in my policing days was done by a wife with a little bitty .25 auto at 22 feet with one shot to the heart. Man sat down right there, told his son that he was a dead man and then proceeded to become one before we got there.
The point is: You can kill someone with a BB gun if you know what you are doing. There are lots of people occupying space in cemeteries with holes in them made by .38 special and smaller rounds. First, learn to shoot!
I learned on a Smith & Wesson Model 10 heavy barrel. Cheap to shoot and cheap to reload and they conceal pretty well. And it is easy for anybody to shoot.
Last lesson: learn to shoot at 8 inch pie plates. Then practice on saucer sized targets out to 7 yards. Become consistent. Learn each move slowly. Don’t try to speed up until you are not missing any shots at slow speed. Practice often.
After all that, I have two weapons of choice: 1911 .45 auto or a Smith & Wesson Model 10.
Get a copy of Bill Jordan’s book “No Second Place Winner” and anything you can get by Jeff Cooper.
Why did the guy’s wife shoot him?
Looks like step #1 is to find a range.