As much as I strongly agree with the sentiment of stopping criminals and helping neighbors, the law is full of land mines for citizens taking actions against criminals.
I poked around a bit and found the law seems nebulous and expanding as cases are settled. That makes it very dangerous since you can never be sure exactly how things will end up.
Here is a link to a California site.
California Legal Opinion
In essence, it says that a criminal being arrested that THINKS excessive force might be used against him has a right to defend himself. In Fleming's case, that might mean the burglar, feeling threatened by a warning shot, could have legally defended himself by shooting Fleming. It sounds crazy and I don't agree with it. But it is law in California.
I even understand it a bit. We have a presumption of innocence. You see a guy doing something illegal, you pull your gun for a citizen's arrest, he bolts and you shoot him. The problem is that he turns out to be innocent. The law addresses this issue by saying that only required force may be used. There's even a question whether you can restrain a person you suspect of a crime. You tell him to stop, he refuses and walks away, you wrestle him down and hold him. You may have used excessive force and illegally restrained him. As Ward Bird found out, this process can be a nightmare.
The law can be a nasty thing. Consider that a person stopping to help an injured person could have been sued for accidentally causing more damage. We had to write "Good Samaritan Laws" to specifically protect them from legal assault.
As I said, some of these interpretations of the law seem to fly in the face of common sense but if you have a police department and prosecutor that lean in that direction you can run into big trouble.