It's weird how he pans around twice just before the plane comes into view. The first time, the people by the railing are just chatting/idling, while the second time, they're looking towards the sky, but just those people. If you pay attention the second time he begins panning, you'll notice a guy in shorts with a navy t-shirt turning his head towards those at the railing, which is exactly when "Kevin" starts turning the camera around. That guy turning around could've been a signal both to "Kevin" and to the guys at the railing, or maybe they were just the only ones that heard the plane.

No one really makes a sound while the plane is above them, except the lady that says "it's crashing" (I think) and "Kevin" that goes "Oh!". They only begin screaming when it blows up. You could argue that they were transfixed by what they were seeing, I suppose.

Then there's the way "Kevin", "My lord", speaks. It doesn't sound natural at all, nor did the other two that spoke to him. They were laughing it off, joking about not going into public buildings. I guess you could argue you never know how people react in this type of situation. Still, suspicious.