Blind Horizon

Blind Horizon is a 2003 conspiracy mystery thriller film directed by Michael Haussman. The screenplay was cowritten by F. Paul Benz and Steve Tomlin. The leading cast includes Val Kilmer, Neve Campbell, Sam Shepard, Amy Smart, and Faye Dunaway.

As the President arrives and prepares to address the public, Kavanaugh attempts to follow what evidence he has to warn the authorities and avert the assassination. While he views the President from a nearby building, he discovers a set of snipers equipment, including a rifle, which he instinctively assembles. Taking aim out of the window, he sights the President through the scope of the rifle, and realizes that he, in fact, is the assassin, and that his flashbacks are of all the preparation leading up to the date of the event. He notices another assassin taking aim at the President with his sniper rifle from the other side. Understanding that he has the power to change the course of events, Kavanaugh aims at the other assassin through his scope and shoots him, killing him and averting the assassination.

Source: Wikipedia