It’s a little sad that local laws really deter people from wanting to help. Heck I’m not allowed to shoot an armed intruder in my house at 2:30am. I have to retreat from the danger. I can imagine what the court would do to me if I shot a mass shooter in the back. “Kento’s you were not in any danger from the shooter, why didn’t you just run instead of using deadly force?”
I'm in Michigan and have no legal obligation to flee an intruder in my home, but I still worry about a woke DA prosecuting a case of self defense. Then there is the civil liability, which has a lower threshold for determining negligence or guilt, especially when the perpetrator's family declares the dead family member had graduated from med school and recently applied for sainthood.
You never know what a jury will decide, though as the cliche goes: I'd rather be judged by 12 than carried by 6.
(I cringed a little bit as I typed that last line, but it's still true.)