check out the secret service guy...

[Maestro232]

Check out the secret service guy going to work after about :20 seconds...

http://cspan.org/Watch/Media/2010/03/19/HP/R/30820/President+rallies+for+health+care+legislation.aspx

[pacelli]

What behavior are you specifically referring to?

[Maestro232]

The SS dude is standing watchfully in upper left, then suddenly takes off into the second row of forward facing seats.