Ask HN: Would something like this work to prevent mass shootings?

I've had an idea for awhile that I think would help prevent some of these mass episodes of violence we've been seeing lately. I personally don't have the resources to implement anything like this but I know there are many engineers out there who do and I just want to put my idea out there to get everyone's thoughts and maybe help improve on the idea. So essentially my concept is that people be equipped with a PPD (Personal Protection Device). You would be required to take a short training class before having one and be licensed and registered. It would use some combination of non-lethal weaponry (stun dart, gas round) and use a smart targeting system where it basically works like a camera and it's point and fire. The target would be "painted" and the the device would figure out the best trajectory to the target. So in the heat of the moment a non-combat trained person would have an easier time using it. After the round is fired and the target is unconscious, the police would be notified and a picture of the target sent to them as well as the GPS coordinates of the device. I imagine if something like this was even integrated into cellphones or something it could become extremely widespread and everyone would have a method to protect themselves that didn't rely on guns alone. I think if adoption rate was high enough then these shootings would become less frequent.

I just wanted to share this idea. I know the technology is out there to put something like this together but like I said I don't have the time or the resources to do it myself. I might have overlooked something as well. What are your thoughts?