Vantage Point - Uhh....What Now?

WARNING - SPOILERS AHEAD

I thoroughly enjoyed Vantage Point, the complex thriller showing the attempted assassination of the US President through different perspectives. However, while watching the movie for the second time I noticed a rather glaring mistake.

It occurs when we get to the tourist's (Forrest Whitaker) take on proceedings, we follow him as he dashes after the secret service agents chasing the spanish cop.

Forrest, on top of the walkway watches in horror as the cop is shot, then turns to see the two secret service agents firing from the side of the road.

(MikeOutWest)

However, when we finally get to the end section and are following Dennis Quaid again, we find it is he who does all the shooting and the two other agents are nowhere to be found.

This raises the question - was Vantage Point so complex that even the director, script writer and editor couldn't keep track of who was meant to be where and when?

We won't mention the speed Forrest needed to run from the walkway to the freeway in order to...