I guarantee the real number is far, far above 37%, but not in a teen's bedroom. An unloaded gun is just a poor club, and a secured weapon is useless, even for a club. There certainly are some, but I am an expert, and I don't know a single gun owner who doesn't keep a loaded, unsecured handgun in the bedroom.
The number of people buying firearms of all sorts has gone up dramatically in the last six years from fear that a democratic controlled government would place more restrictions on certain types, including handgun.
Teens can legally own a gun, but can't actually buy one until he's eighteen. I started hunting at age seven, and owned my own rifle and shotgun at age eight. I also had full access to a revolver at age ten. This really isn't uncommon, but it is uncommon to have a handgun stored in a teen's bedroom. Technically, it isn't illegal in the majority of states, but it can be used against the parents, should something bad happen, be it accidental or intentional.
The psychological part is difficult. I can't remember a single case of one teenager shooting another in his own home out of fear. We've had a number of accidental shootings, but that's about it.
In most states, you can legally shoot someone for three reasons. 1. If you legitimately feel your life is threatened. 2. If you have reasonable belief that you will suffer severe physical injury. 3. In defense of property.
If this is a gun owning family, it is possible, even likely, that a teen would have a rifle and shotgun in his own bedroom. It's somewhat unlike, but possible, that he would have a handgun.
We started hunting at the same age.
There are only a few states where protection of property, by itself, is justification for lethal force. Texas is one. Gun laws are all over the map in the US. My wife's and my carry permits are good in 37 states. It requires study when we take a trip. We have both taken several classes and read a number of books related to the rules of engagement for self defense.
I was raised in a hunting family. My Dad carried a concealed gun (.25 caliber Colt vest pocket gun) for a few years because of death threats (when he was a lawyer working for the OPA during WW-II).
I was also in the Army.
My home has lots of guns. Everybody in my family has a concealed carry permit (except the two in California) including the kids who are all moved out and married. The only loaded gun in the house that isn't in a safe is the one on my hip (a SIG C3 as I type this), or my wife's hip when she's packing. The bedside safe which contains two loaded guns is unlocked when we go to bed, locked when we get up. The kids never had guns in their rooms.
A lot of authors get gun stuff totally wrong.
The time (year) makes a difference with regard to the story - so does location. Now, a gun in a kids room, in the city would be rare. Especially in the north east. On a farm, possible, even probably if the kid is eleven (the minimum hunting age in PA) or older.
Back in the day, late 1940s and 1950s I had a .22 rifle (Winchester Model 52 Sporter), a handgun (.22 Colt New Frontier single action) and a shotgun (Fox .410 double) in my room as a kid (I was born in 1942).
My friends had guns in their rooms. We didn't mess with them. We had no curiosity because we all had been taught gun safety - I'd shot all my best friends guns, he'd shot all of mine, when we were out with our fathers. To this day I can't pick up a gun with out habitually checking to be sure it's unloaded even after the clerk in a gun store has just checked it.
During hunting season more than one student car in the parking lot had a deer rifle and ammo in it because we were going hunting after school. Nobody panicked. It was normal.
It would never have occurred to us to shoot a person with one. That was what bad guys did. We weren't bad guys. We didn't want to be bad guys.
We had books, we didn't have TV until I was a senior in HS.
Fitch