Why didn't Secret Service jump in front of the shoe?

Factual Questions
41

Little did Bush think when he said, “Bring it on!” that the “it” would include P.F. Flyers.

42

Bush: …and furthermore, ladies and gentlemen,
Secret Service Agent: Look out, he’s got a SHOE! tackles the President
Bush: Whew. That was a close one. Anyway, I would just like to say…
Secret Service Agent: SHOE!! tackles the President
Bush: Ugh. Anyway, as I was saying…
Secret Service Agent: LOOK OUT, A SHOE! tackles the President
Bush: Now cut that out! I think you’re doing this on purp—
Secret Service Agent: A SHOE! tackles the President