This is a really bad idea with a handgun. As Trebor noted, a skilled fighter can engage the shooter within up to 21 feet before a typical shooter can react. I wouldn't take someone's gun away at 2 feet, but I would likely break their fingers in the process of deflecting it, and they would almost certainly not get a shot off to even miss.
There have been plenty of FoF drills similar to that where one guy has been the defender with a gun and the other one has been e.g. the attacker with a knife. It can be surprising just how good one has to be with, say, a pistol to get in even one good shot when a determined opponent charges in with a blade from 10 feet with intent to kill. 2 feet... the 14yo better be a great shot and the only way to get those skills is doing dry fire drills as often as possible, preferably daily, and go do some actual shooting at the range about once a week and even then shoot IPSC (or preferably something even better suited for practicing combat shooting) or some such instead of just shooting one target from 25 meters. I've found that the old adage "practice doesn't make perfect; perfect practice makes perfect" to be quite true when it comes to effective combat shooting.
If you need to use a gun, you need to kill someone. If you don't need to kill them, don't use a gun.
I agree that that is the general consensus among "normal" people but if the character is callous or perhaps a "teflon" (i.e. a certain specific kind of a psycopath who is unable to feel emotions such as pity, sympathy, empathy, and though may understand the concept of remorse and shame, is incapable of feeling them), well, I could see how such a person would shoot someone even without immediate risk to their own lives (the justification in such a character's head could be along the lines of "well, he threatened my health without provocation first and though he only intended to hurt me, that alone is reason enough for me to cause them permanent damage." You know, the kind of justification where someone thinks that because someone punched you once, since they instigated the matter, you would be justified in punching them twice in retaliation because if they hadn't made the first move, the situation wouldn't have come up in the first place). For instance, a gutshot
can leave a person badly wounded and in serious pain but alive for hours upon hours (and even then, when death finally comes, the point of a "clean, dignified death" is likely long gone).
Those are just food for thought, ideas for various character types. I've written a teflon into one story and hence did some research on such people and what motivated them to do whatever it was that they did. It's surprising just how many of the real teflons enjoyed torturing and killing animals when they were kids. There was a local incident some 20 years ago when two 12yo boys kidnapped a 6yo from a grocery shop, took him to some abandoned house, basically tortured him to death, left the body on train tracks, and then went for a pizza.
And then there's the less calculated reactions to a physical threat: someone who's not familiar with violence and the way adrenaline affects their mind and body might freeze or go overboard (for example) when under the threat of physical harm, i.e. a guy threatens to break your nose and you put two rounds in his chest. Or if emotions run otherwise high (e.g. like what happened here in Finland: a random guy sees another guy trying to rape a woman and he gets a bit carried away with the beating and got charged with assault himself even though he didn't even cause permanent damage to the would-be rapist... yeah, we don't have a justice system, but a "justice" system).
Then again, how is one to know if an assailant
will stop just at breaking your nose even if that was his verbal threat prior to the physical attack? Just as an example I could recount an incident that happened to me: I was out jogging with my wife, (K. Trian here on AW) it was a late afternoon, a bright day, and we were going through a nice neighborhood with expensive houses when I spotted three guys before us. One had fallen into a ditch, one was helping him up, and the third was just standing around with his back to us, all three of them drunk. There was a small bridge we needed to cross but when we passed the guys, the third suddenly tackled us against the railing with no prior warning. I shoved him to the side to give enough room for the wife to pass and move on (we've agreed long since that should something like this happen, I will deal with it and she will run to safety and if need be, call the police). Once she was in the clear, I found myself using the fence (Geoff Thompson's concept, search for it in youtube if you don't know it) to keep the guy from getting any closer than an arm's length (he was constantly moving forward and twice I had to shove him back while I assessed the situation). At this point his two buddies were back in the game and about a yard behind the lead jerk.
That was when I was faced with a conundrum: the guy before me was obviously aggressive, itching for a fight, I had no way of knowing whether his friends would join in should we tussle, and, of course, I had no way of knowing if any of them were armed in any way. All I knew was that there were three of them, just one of me, that at least two of them were bigger/more muscular than me (and I'm 6'1/185lbs & athletic) and they wanted me no good (it was impossible to gauge whether just one of them wanted to slap my face once or if all three of them intended to stomp on my head until it was flat). That's when I decided that should the main antagonist step close enough that my lead hand would touch his chest a third time, I'd deck him.
Luckily, I managed to resolve the situation verbally (asked if there was a problem, not sure if any of them caught my other hand hover close to my waistband) but the situation could have easily escalated due to several things (e.g. if I'd appeared less determined, if they'd been in a more aggressive mood, more drunk, less drunk, whatever).
I think a person needs to have a few simple plans (A, B, C etc) in case for such situations: you have your plan A (e.g. try to de-escalate verbally), if that fails, plan B (e.g. pre-emptive strike and leg it), and if that fails, plan C (e.g. lethal force), and all of those plans should come into play when a specific trigger has been engaged instead of by conscious thought (e.g. my trigger for plan B in that situation was if the guy had moved close enough that my lead hand would have touched his chest a third time) because sometimes an adrenaline dump can impair a person's thought process and that's when pre-learned triggers can be the dividing line between a mental lockjam/freezing and action.
I'm rambling now, aren't I? Sorry about that. I'm interested in self-defense (I hate that term btw because it's so passive) in general and have found some of these things quite useful when writing scenes of violence into a work of fiction. It might also be a good idea to google names like Geoff Thompson, Southnarc, Richard Dimitry etc. for good material and read some real accounts of violent lives (like aforementioned Thompson's autobiography, Watch My Back) if one strives for realism in fight scenes. Of course first-hand info is always a notch more authentic than second-hand stuff but the latter is safer and exposing yourself to the former on purpose is just... not worth it. Okay, I'll shut up now.