Maybe. You don't know how this guy, in a sleep induced state, reacted to this break-in under stress. Surely he could have forgot to flip off the safety. Maybe he was raising the gun and about to flip it off when he got shot. I haven't heard if the guy's seen combat. Maybe he flipped the safety off and as he was getting shot his hand flinched and flipped it back on safe, maybe his body twisted as he shot and he fell on his firearm and it switched off...stranger things have happened. All speculation...all we know is that the weapon was found on-safe. Doesn't mean that in .24 seconds he wasn't about to flip it off and start shooting.
You realize this man was a Marine right? That alone should tell you one thing. He always knows whether his weapon is on safe or not. His hand is not going to "flinch" the safety to the "safe" position on that particular weapon system after being shot. If anything, he would have moved it from "safe" to the "fire" position. Just the way you are trained when shots are fired.
Had the weapon been pointed at the police, his weapon wouldn't have been on "safe". Marines are trained that when you point a weapon at something you intend to kill it. Which means as the weapon is raised you put that weapon into fire mode, just as Dross pointed out.
Whether or not he has seen combat is the part that is irrelevant. Marines train with M16's and M4's for their entire military career. They know how to work the weapon and they abide by the safety rules.
It seems pretty obvious to me he had no intention of shooting at whoever was breaking into his home, but rather subdue them. Otherwise that rifle would have been firing as the door opened.
Was he fully awake(?), well trained with un-deteriorated skills(?), battle tested, good under stress(?)
Fully awake? Yes, you wake up pretty fast when your family and/or your well being is at risk.
Well trained? He was a United States Marine. Need I say more?
Battle tested? He may or may not have seen combat, but Marines train with live rounds.
Good under stress? Every Marine is good under stress and great when they have a familiar weapon at their side.
Now, I won't state my feelings on the matter since it could raise a big stink. Nor will I defend the police or say that their reports are a lie but I will defend all Marines when their skills are put to the question and they are not here to answer for themselves.
So please, if you're saying it is his purely his fault that this happened, step into his boots a time or two.