Comes a Horseman: Robert Liparulo

Two FBI agents are called to investigate a string of murders where a seemingly random selection of people have been attacked by dogs and then decapitated. They then find themselves as the next to be stalked and both narrowly survive the attacks. They uncover a centuries old cult who believes they need to follow the antichrist to become powerful. A psychopath leads them to believe he is the antichrist and sets out to murder people who claim to have died and seen hell and people who get in his way. In the end the cult "the watchers" have a gathering and they are able to kill the "antichrist" before he continues his murdering rampage.