I'm glad you're so worried about the criminals breaking into a house.
I think he/she was trying to protect you. The crook can actually sue you even though they were committing a crime. Terrible law, but true.
You also might kill a fireman, or a policeman. The bullet could ricochet and kill a neighbor. You or someone else that you forgot that you gave a key to could get killed. Too many ifs.
The sad part is that lights, motion sensors, non of that stuff really works. What you want to do is to make it as hard as possible so maybe they will move along to another house.
I always like to have a family member or trusted friend to stay at my house. (Especially nice if it someone a little older to likes to stay in all the time!) Stock the fridge well, add some personal touch that they like, such as favorite wine or crafts to do, or ??? Sometimes an Aunt will use this as retreat time to take a break away from an Uncle.
You 2nd best defense is noisy neighbors!
You can also call your local police and have them do a vacation watch.
You can have the post office hold your mail, (but sometimes I wonder if that is the best idea).
Other great tips;
Reinforce the jam plates on your doors to help prevent the door being kicked in.
Use the dead bolts with the extended (longer) bolt.
Install a key only deadbolt to be used ONLY when you are on vacation.
(Unsafe while at home). You don't want them to go in a window and out a door. A moving truck loading items out a window draws much more attention!
Install a solid core door from the garage to the house. Reinforce it as you would an outside door.
Do not have a knot or handle on the emergency cord of the garage door opener. Burgulars will often slide something into the sides of the door, hook the strap and open the garage door this way.
Put locking pins on both sides of the garage door. You don't want them hiding inside the garage working on getting in the house door.
BTW- all door hinges should be on the inside of your home!
Install pins in all windows in addition to locks. (Double pane windows make more noise and are harder to cut through than single pane window).
Keep the yard well lit.
Keep tall shrubs away from windows. ( So crooks can't hide behind them.)
Put pins in sliding glass doors so that they can't be lifted out of the tracks.
Put a padlock on the yard gates, so items have to be lifted over, or they have to take the time to cut the lock.
If you can, put a fence around your driveway as well as your yard.
If you can, always keep your cars in the garage, so it is harder to tell if a car is gone.
If you fly, and your car is not normally in the garage, consider using a shuttle to take to the airport and leave the car in the driveway.
Ask a trusted neighbor to park an extra car in your driveway.
Most people have privacy fences, but actually a neighborhood with cyclone fencing allows neighbors to watch out for each other.
Organize a crime watch in your neighborhood.
Keep a large ( that can be seen from the street) "No Solicitors" sign on your door, porch or mailbox.
Don't hide valuables in the bedroom.
Buy a safe! They may be able to get into it, but it will slow them down.
Remember to secure your bank statements and other personal information in a safe so that you do not become a victim if identity fraud a year after you were burglarized!
An alarm might scare off kids or the non pro. (I have also heard that some crooks look for houses with alarms thinking they have "better stuff" and knowing the response times of police in large cities can be slow.) But IMO the best part of an alarm system is to possibly alert you earlier to a break in, giving you a clearer head and better aim.
Of course if you can afford it, nothing like camera monitors installed in the home that you or your neighbor can watch via the Internet! The best security systems are battery backed up and use wireless to transmit so that they will still call when the phone and power lines are cut.
That is what I can think of just off the top of my head. (I am lucky, in Texas you can protect your property with deadly force.)