Given the kid had a real gun and was firing into the crowd, and given Secret Service goons were putting their heads in line of sight to protect Trump, I find it really hard to believe they stood down as a unit. Maybe one sniper thought "nah I'll just pretend I didn't see that", but orders from above seems unlikely, unless the goons were given assurances that the sniper would not hit them, which in turn implies the kid was under order.