The main idea of any safe or storage cabinet is to delay access to any unauthorized person trying to get into it. The bigger, the heavier, the better the safe, the longer it will take to get into it. Hopefully, it will be enough trouble, that the unauthorized will either not attempt to get in, or will find it to be too much trouble and give up. This will usually deter a casual thief, such as one seeking drug money.
A very determined thief will figure a way to take the safe away and open it at their leisure. The best discouragement to this is to bolt the safe to the floor, the wall, or both. This will also make it more difficult to tip the safe over to use pry bars on the door. It's harder to pry the door open with the safe upright.
With a troubled youngster in the house, most acts will be impulsive, and it may be enough just to delay access for a while. If the youngster/teen is shown to be violent, hateful, and/or determined to be hurtful, all fire arms must be removed from the home early in the process. Do not trust any safe, cabinet, lock box, or trigger lock. Get the guns out. Ammo too.