 They had an assault on a protectee. The agents moved in to cover the protectee and basically form a body bunker at a protectee because in the world of protection, it's your body that is the protection between the threat and the protectee. The agents then figured out where they were going, which in this case, they were moving to the motorcade. They probably did a quick assessment of the former president while he was on the ground, asking him if he was okay, checking him. They probably saw the blood, but it wasn't a major concern.