From a pre-crime stand point, bad idea to stop things from happening that way or going back in time to prevent a bad event. If so then some future event might not be motivated to happen or someone may do something with terrible consiquences that may not have otherwise been done. I know the movie you mean I think.

This was a terrible event that could have easily been prevented but the safety barriers were not where they were supposed to be.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!