It's a small town. In small towns nothing much happens. So he was taking a video of probably the only thing to happen around there in a decade. He had no idea it was going to explode and he was far enough away that he also thought he was safe and not in the way of the authorities working the fire.
So I don't blame this guy at all for what happened to his kid, who I really hope just had temporary hearing loss. And also, his first reaction was, "Are you okay?"
I don't think he took his kid to watch it...he was driving and pulled over. On the other side of things...if you see the force from the explosion in the video...it is probably a good thing that he was parked and not driving and the act of recording that video has the potential to be an act that saved his and his child's lives.
Also I don't know the story entirely or all of the details...but when I drive by a building...I don't assume it is a super explosion hazard nor do I know what every building's specific contents are. He really could have thought he was just recording a very large fire.