The Standoff at Sparrow Creek (movie, 2019)

After a mass shooting at a police funeral, reclusive ex-cop Gannon finds himself unwittingly forced out of retirement when he realizes that the killer belongs to the same militia he joined after quitting the force. Understanding that the shooting could set off a chain reaction of copycat violence across the country, Gannon quarantines his fellow militiamen in the remote lumber mill they call their headquarters. There, he sets about a series of grueling interrogations, intent on ferreting out the killer and turning him over to the authorities to prevent further bloodshed.