Well if the " terrified " bit referred to " over-egging " there'd have been no need for a 999 call, so he ,NB, was either terrified or he wasn't. What do you think the call sounded like ? Always supposing that you believed that there was a call-----most don't.
But it's not about what WE, in the here and now, think. It's about how Jeremy reacted to an alleged -and frantic- call from his father at silly o'clock, telling him Sheila had gone mad and got hold of a gun. Jeremy, it seems, sees no urgency in the situation -didn't he state as much- do calmly diddles his way through a few of the local police stations, making abortive calls, phones Julie, then phones the police, at which point he changes his mind and tells them his father had sounded terrified. Did he not later tell someone that it was possible that his father had already been shot?!!!! But it wasn't urgent!!!