Moral of the story...don't bring a knife and brass knuckles to an AR-15 fight.

Three teens who broke into a house in Oklahoma were reportedly gunned down by the 23-year-old son of the homeowner after he opened fire with an AR-15 semiautomatic rifle.

Law enforcement officials later determined the bloodshed Monday night in Broken Arrow, Okla., was self-defense, although an investigation was continuing, The Washington Post reported.

The home invaders — a 16-year-old, a 17-year-old and a man thought to be 18 or 19 — planned to burglarize the home, smashing open the back door, the Wagoner County Sheriff’s Office said in a statement posted to Facebook.

One had a knife and another had brass knuckles, the Tulsa World reported.

Two of the teens died inside the kitchen of the home; the third "was able to run to the driveway before succumbing to his injuries," the sheriff's office said.

The suspected getaway driver, Elizabeth Rodriguez, turned herself in at the Broken Arrow Police Department, the Tulsa World reported.