“I carried an M4 in the military. It was a very scary thing to see just how efficient and powerful and dangerous it was. It was developed for one reason – to be a weapon of war made for creating carnage and doing so in a way that you don't have to stop to reload.”

Over the past few years he watched aghast as these kinds of high-powered rifles were turned on innocent people in attacks across America, from Sandy Hook to Las Vegas. And then, on Valentine’s Day, a gunman attacked the Stoneman Douglas High School in Parkland, Florida, killing 17 people.

“I think when Parkland happened, it was a breaking point,” Kyle says. “This was maybe the sixth mass shooting to happen using the same rifle, the AR-15, the civilian version of what we carried.”