If he really didn't go back to help I don't think there is a question of whether or not he fucked up. As far as he would have known he's the only person on the scene qualified to administer first aid. However, again, no one knows for sure what happened yet because it's been 4 months and as far as I can see we have gotten no new information since.

I will say that you'd think if the cop actually went back to the house and did help, contrary to what the family is saying, the police would have release the dashcam recording on his car showing he went back. As far as I can tell the footage still is not released. Unless it has been released, I see reports that they have dashcam footage but I haven't been able to find it.