With time-traveling capabilities, the FBI sends a self-centered agent to observe and report the gruesome murders of a prominent family, but as his feelings begin to change will he have the strength to leave the past alone.

This sounds very much like Deja Vu or Source Code. What is it that will make it different? You have the idea down but think it needs trimming. Try and find a way to use single words where you have used two and perhaps take out the prominent family bit and just replace with notorious murder or infamous murder. That way people know it was a big deal and uses less words.

Also nitty picking….. question mark at the end lol.