My life is worth more than that - to me. It's obvious, from having that gun in your face, that it's not in battery by quite a bit. Seeing that major advantage right away, is the reason to act on it - because your life is probably worth more than that, too - everybody.
If you don't know how to disarm someone in a situation exactly like that, or wouldn't feel comfortable attempting it - then it's time to seek out training on that exact scanario. This isn't going away, brothers, not in the least. It's only going to become more common.
It's a very good thing - potentially, very lucky thing - that the fucking idiot doesn't know how to load a semi-auto pistol properly, and completely caused his own loading problem - the way he was monkey-fucking that trigger.