El Paso man Jose Manuel Guzman, who has a rap sheet as a drug dealer, was sleeping with his sister.
In his defense, Guzman only recently learned he had a sister, as they didn't grow up together.
What comes next is less defensible.
After learning that his sister was also banging somebody who wasn't her brother he became enraged and beat her to death with a baseball bat in the home they shared.
He tried to mop up the blood and flee the home as law enforcement approached, but he wasn't able to get away.
He's been charged with murder and is being held on a $1 million bond.