New Theory from Andrew.
A lot of people are suggesting that A) The future's people saw might not be written in stone, and B) The visions probably don't take into account that they saw these visions.
That's just not true though. The FBI agent saw himself working on a case about the visions. That means that the visions take into account that the participants have seen the visions, and if that's true then they would also take into account any actions people might have taken to stop their visions from coming true. This means that history will play out like people have seen. Nothing can change, or else they would have seen things as different.
Spot on mate. Thats exactly what I've been thinking. They can't change anything because the future they saw was a result of them trying to change things. In the future they had already tried to change things because of the flash forward and that is where they ended up. They are destined to react in the same way and thus cause the future that they saw.