Spot gives him an unimpressed look, but bites back something sarcastic - his usual attitude might work to keep the kid quiet, or it might send him running to tell the world what he's seen.

"...how?" he says eventually, because the curiosity is overwhelming, and he doesn't believe for a second that the kid wasn't responsible for what just happened.

It doesn't occur to him, yet, that there might be a level of mutually assured destruction here - they've both got secrets they want to keep.