15 shots does not sound random
Unfortunately, these days all of the "bad guys" have gotten 3D printed "switches" for their Glocks, (internet, dark web, etc).
Absolutely illegal to possess, but the bad guys scoff at the law these days...... and if you are not supposed to have a gun in the first place, the last of your concerns will be the switch attached to it.
The 3D switches, turn a semi-automatic pistol into a full auto, so if they hold the trigger down, their 15 round magazine is empty in about 2.5 seconds.
That is probably a more likely scenario, with them deciding to "spray and pray" their ammo, as they ran away. If some asshole was going to take the time to shoot 15 separate rounds, with 15 subsequent trigger pulls, at Jake, even a child would have probably had better luck hitting their intended target.