[He won't even see this for now - knows what Arthur would say, knows the kind of measurements he'd take. It hardly matters to him, he knows he can't do a lot of things he'd want to, knows he can't prevent Arthur from being as upset as he will be, that he can't explain much to Morgana either...]
[He's left, left Arthur's side for once - and that alone should be enough of a hint of how shaken he is by this. He's withdrawn to the woods, like the time when Gwen arrived and he just wanted to hide. Except he's hardly hiding, and in fact it'd be pretty easy to realize he's there, or that someone is at least, as his idea of dealing with this and letting off steam is... rather difficult to ignore.
He's using magic, and his powers never were the type to go out of control due to emotions (as Morgana's or Mordred's were), no, this is perfectly calculated fury, blasted at trees that are being set on fire, at the ground which he shakes a few times, much like he did when he was a literal dragon some months ago. Except he doesn't have the excuse of fear for people's safety and his actual size to justify it this time. He's only angry. And hurting.]