It's a full life, if a trifle banal

I think it could be done, assuming neither the runner nor the bulk of the crowds were equipped with radio earpieces. It's just that the commentary ought to have switched to "He's still running! They're still cheering! They have no idea of the disaster that has happened here!" And you'd see stewards or something trying to fight their way to the front of the crowd to explain. But as communicator has said, there was a rather childlike naivete about how the real world would react throughout the story - she cited the absence of police and press investigating the disappearance of several children from a well-heeled estate.