4 masked men break into your house, at that point you don't know anything about them. You don't have time to sit down, interview them, look into there background, find out there motives and there plans. You also don't have a time and probability machine to see what happens if you do one thing or another. There is no quick save/load function available...your left with what's happening, 4 masked men breaking into your house.
The adrenalin stars pumping, that's it, it's fight or flight, you grab a knife you thrust, maybe you hit, maybe you don't, do you care? No, they could be armed, you remove the threat. What if you don't? What if you graze him and he comes back at you with a knife himself? You lost your only opertunity. What if he runs off, he could come back and that won't do, your still not thinking straight, so you run after him.
We aren't talking about reason, your in a panic, adrenalin is working, your brain is working with it's lower functions.
They made the choice, they did so in the cold light of day, they had chance to think about what they did, the person getting burgled didn't.
Unless your trained and your body and mind are used to this kind of thing where you can keep your decisions in the higher levels of your brain your going to do what comes naturally, your going to protect yourself, be that running away or fighting and damn those that get in the way.
All that said, the police are just following procedure, find out what happened and then make a decision.