Well, homicide and murder are definitely not the same thing, but I've talked to many people who don't realize that. I think a lot of people think of them as interchangeable terms, like it sounds like you do, right? But I hope you'll stop thinking that now, because I'm sorry but it's wrong!
Any killing of a human by a human is homicide. Sometimes it is murder. But not always. It's even called homicide when it's legally excused (sanctioned by law), and no criminal charges are filed. Like self-defense. And cops using lethal force, providing it was necessary. And executions. Those are all justifiable homicides. So when you think of all homicide as murder, you're leaving out all those kinds of homicide.
Then there's criminal homicides. But not all those are murder either! The various terms differ depending what state (or jurisdiction) you're in, but manslaughter is the non-murder criminal homicide I think of first. And it can be voluntary or involuntary. Then, of course, as you know, some criminal homicides are murder of one sort or another (1st degree, 2nd degree, some places have 3rd degree, then there's what's called felony murder, which is oddly named since all murders are felonies...)
Back to the case under discussion, they're going to have to decide what kind of homicide they'll call this. If it were up to me, I would definitely call it criminal homicide, but I can understand why they might not call it murder. But they might! If it weren't for the fact that he shot THROUGH the door, I think the homeowner would have a lot less to worry about. That is not what a reasonable person would do, imo.
To be called murder, the intent to kill (malice) must be present. So that's a sticking point in my mind. Because yes, we know the homeowner intended to kill (or harm) when they fired their gun, but they didn't intend to kill or harm an innocent person who just had the wrong address. They intended to kill or harm a dangerous home intruder. So if the prosecution feels they can "transfer" that malice, they may charge with murder. It'd be a lot harder conviction to get, imo, if only they didn't shoot thru the door. That and the fact that they'd already called 911, so help was on the way.