This reminds me of when the house I was living in was shot.
I was renting a room from a guy who owned a townhouse. It was me, the owner, and one other dude who was a veteran. Anyway, we had neighbors next door, a single mother, her son, and his best friend. Now the mom worked about an hour away and was never home, and the two boys were about 18 years old or so. That age right after they graduate highschool but still hang around at the highschool and it isn't weird because that's where all their friends are. Apparently they were selling weed there and such, which due to the lack of supervision was kind of expected, but we didn't care because they never bothered us.
That was until one night our house is shot in a drive by. Apparently they must have ticked someone off, because some kids do an amateurish drive by shooting of the neighbors house, but also our house too. We weren't sure if the shooters knew where the neighbors lived since they shot both houses. And we knew those two teenagers knew the shooters because they were bragging about the fact their windows were shot out. My roommate who owned the house was scared and called the cops but they wouldn't do anything for some reason, and the security system he had obviously did precisely jack dick as we didn't realize the house was shot until the next morning. We figure if the neighbors were going to keep doing stupid stuff, the next step might be a home invasion. The owner installed new security cameras but I wasn't putting any stock in that since we already had cameras and they did nothing. So, I decided it was time to buy a gun. I knew my veteran roommate had a little .38 he kept on his desk so I asked him for advice and I ended up going with a 9mm.
When I brought it home I was reading through the literature as my roommate is inspecting the gun. I asked if I should keep it locked up for safety. He walks out of the room and comes back with his .38 Beretta, racks the slide, and a cartridge falls out. He says, "You keep it loaded, you keep a round in the chamber, and you keep it within reach."
Moral of the story is, we had motion lights, we had cameras, we had a security system, and they didn't really prevent anything from happening. It's a good idea to have a firearm.